Frequently Asked Questions
About Seritex
Who is Seritex? Seritex has been the exclusive authorized North American importer and distributor of GPM (Switzerland) and Holtain (Wales) anthropometric instruments since 1986. We are the only authorized source for these instruments in the United States and Canada. Every instrument we sell is sourced directly from the manufacturer, carries a full factory warranty, and is supported by our specialist technical knowledge.
Can I buy GPM or Holtain instruments from other U.S. suppliers? No. Seritex holds the exclusive North American distribution rights for both GPM Instruments (Gneupel Projects & Mechatronics) and Holtain Ltd. Any GPM or Holtain instruments offered by other sellers in North America are either sourced through unauthorized channels or are being resold without manufacturer authorization. Purchasing through unauthorized channels may void the factory warranty and means you will not have access to manufacturer-backed technical support or calibration services.
How long has Seritex been in business? Seritex was established in 1986 and has been continuously operating as the exclusive North American distributor of GPM and Holtain instruments for 40 years.
Ordering and Payment
Do you accept purchase orders? Yes. We accept purchase orders from universities, hospitals, government agencies, military programs, and research institutions. Visit our Institutional Buyers page or email info@seritex.com to set up an account.
What payment methods do you accept? We accept credit cards (Visa, Mastercard, American Express), purchase orders with NET30 terms for approved institutional accounts, wire transfers, and prepaid checks.
How do I request a quote? Use our Request a Quote page, email info@seritex.com with the instrument(s) and quantities you're interested in, or call us at +1 (201) 755 4213. We respond to quote requests within one business day.
Do you offer NET30 terms? Yes, for approved institutional accounts. Contact us at info@seritex.com to apply for NET30 terms. We will need your institution's name, billing address, and a purchase order or credit reference.
Are you registered on SAM.gov? Yes. Contact us for our CAGE code, DUNS/UEI number, and other government procurement details.
Do you offer bulk or volume discounts? Contact us to discuss pricing for multi-unit orders or institutional equipment packages. We work with each client to accommodate budget requirements, especially for universities and research programs equipping labs with multiple instruments.
Shipping and Delivery
Where do you ship? We ship throughout the United States and Canada. We also handle international orders on a case-by-case basis — contact us for international shipping quotes.
How long does shipping take? Most in-stock items ship within 3 to 5 business days via UPS or FedEx. For instruments that are manufactured to order by GPM in Switzerland or Holtain in Wales, lead times are typically 4 to 8 weeks depending on the instrument and current production schedules. We provide estimated delivery dates at the time of order confirmation.
How much does shipping cost? Shipping costs vary by order size, weight, and destination. Shipping is calculated at checkout for online orders. For quote requests and purchase orders, we include shipping costs in the quote.
Do instruments ship from the U.S. or from overseas? It depends on the instrument and current inventory. Some items ship from our U.S. location. Others ship directly from GPM in Switzerland or Holtain in Wales. In either case, Seritex handles all customs, import logistics, and delivery coordination — you receive a single shipment with full tracking.
Products and Instruments
What is the difference between a GPM anthropometer and a Holtain Harpenden anthropometer? Both are precision anthropometers used for the same types of measurements, but they differ in design and construction. The GPM Anthropometer (Model 100) uses four interconnecting metal tubes with millimeter engravings and a sliding branch holder with a scale reading window. It has a measuring range of 0 to 2,100 mm and can also be used as a large sliding caliper. The Holtain Harpenden Anthropometer (Model 601) uses Holtain's proprietary counter mechanism for readings and has a different mechanical design. Both are cited extensively in research literature. The choice often depends on which instrument was used in prior studies at your institution or which is specified by your measurement protocol.
Which skinfold caliper should I buy? The Holtain Tanner/Whitehouse Skinfold Caliper (Model 610ND) is the reference standard for many published body composition equations and is the required or recommended caliper for several certification programs including ISAK. If your work involves applying established skinfold equations or you are pursuing ISAK certification, this is the caliper to use. Using a different caliper may introduce systematic measurement error because different calipers apply different jaw pressures.
What instruments do I need for ISAK certification? For ISAK Level 1, you need a skinfold caliper, a small bone caliper (bicondylar), and an anthropometric tape measure. For ISAK Level 2 and Level 3, you additionally need an anthropometer, a large sliding caliper, and a segmometer. The GPM Large Instrument Kit (Model 113) or Complete Kit (Model 113C) paired with a Holtain Tanner/Whitehouse Skinfold Caliper covers the requirements for all ISAK levels.
What instruments are used for military body composition assessment? This varies by service branch. The U.S. Army and Marine Corps use skinfold caliper protocols measuring at multiple body sites. The U.S. Navy uses circumference-based measurements. For most military applications, a Holtain Tanner/Whitehouse Skinfold Caliper (Model 610ND) and a Holtain Harpenden Stadiometer (Model 602VR or 603VR) cover the essential requirements. Contact us if you need guidance on equipping a specific military program.
What instruments do I need to set up a university kinesiology lab? A comprehensive kinesiology lab setup typically includes an anthropometer (GPM Model 100 or Holtain Model 601), a wall-mounted stadiometer (Holtain Model 602VR), a skinfold caliper (Holtain Model 610ND), spreading calipers in both small and large sizes (GPM Models 106 and 108), a sliding caliper (GPM Model 104), a bicondylar caliper (Holtain Model 604), and calibration tools (GPM Model 219 and Holtain Model 602CR). The GPM Complete Large Instrument Kit (Model 113C) bundles many of these instruments at a lower cost than purchasing individually. Contact us for a customized lab equipment quote.
Do you sell anthropometric tape measures? We currently specialize in GPM and Holtain instruments. Contact us about tape measure availability or recommendations for compatible tape measures to complement your instrument set.
What is the Kahn Abdominal Caliper used for? The Holtain Kahn Abdominal Caliper (Models 609 and 609XL) measures abdominal sagittal diameter — the front-to-back depth of the abdomen. This measurement is used as an indicator of visceral fat and cardiovascular risk. The standard model has a 36 cm range; the XL model extends to 50 cm for larger subjects.
What is the Prader Orchiometer? The Holtain Prader Orchiometer (Model 712) is a set of graduated ellipsoid beads used to estimate testicular volume by comparison. It is a standard tool in pediatric endocrinology for assessing pubertal development and diagnosing disorders of sexual development.
Calibration and Maintenance
How do I calibrate my instruments? For calipers, use the GPM Caliper Checking Gauge (Model 219) to verify accuracy against known dimensions. For stadiometers, use the Holtain Calibration Rod (Model 602CR) to check the reading against a known length. We recommend calibrating instruments at the start of each measurement session and documenting calibration results as part of your quality assurance protocol.
How do I clean my instruments? GPM instruments should be cleaned with a soft cloth and mild cleaning solution. Do not use acetone or acetone-containing cleaning agents on GPM instruments, as these can damage the materials. Holtain instruments can be wiped down with standard disinfectant wipes. Avoid submerging any instrument in liquid.
Can I get my instruments repaired? Yes. Contact us at info@seritex.com to discuss repair or refurbishment of GPM and Holtain instruments. As the authorized distributor, we can source replacement parts directly from the manufacturer and coordinate repairs.
How often should I replace the counter on my Holtain stadiometer? The mechanical counter is a wear component that can lose accuracy with heavy use. If you notice the counter sticking, skipping, or giving inconsistent readings, it's time for a replacement. Replacement counters are available for both the 600 series (stadiometers) and 700 series (infantometers). For programs that use their stadiometer daily, we recommend inspecting the counter annually.
Technical Questions
What is the Frankfurt Horizontal Plane? The Frankfurt Horizontal Plane (also called the Frankfort Plane) is an anatomical reference orientation used to standardize head positioning during measurement. It is defined as the plane passing through the left porion (the upper margin of the ear canal) and the left orbitale (the lowest point on the margin of the eye socket). When the subject's head is positioned so that this plane is horizontal, measurements of head height, facial dimensions, and standing height are standardized and comparable across studies.
What is the difference between spreading calipers with rounded ends and pointed ends? Rounded ends are used for measurements on living subjects — they are more comfortable and safer against skin. Pointed ends are used for measurements on skeletal material (bones and skulls) where the tips need to contact precise anatomical landmarks that may be small depressions or ridges in bone. If you measure living people, choose rounded ends. If you measure skeletal material, choose pointed ends. If you do both, you need both.
What does "mm graduations" mean? It means the measurement scale on the instrument is marked in millimeter increments. A reading of 1,742 mm means 1,742 millimeters, or 174.2 centimeters, or approximately 68.6 inches. Most anthropometric instruments read in millimeters because this provides the resolution needed for research-grade measurements.
What is Technical Error of Measurement (TEM)? TEM is a statistical measure of the precision (repeatability) of a measurement. It quantifies how much a measurement varies when repeated on the same subject by the same or different observers. ISAK certification requires candidates to demonstrate TEM values within established thresholds for each measurement site. Lower TEM indicates higher precision. Using high-quality instruments with consistent mechanical properties is one of the most important factors in achieving low TEM.
Still have questions?
Contact us at info@seritex.com or call +1 (201) 755 4213. We're available to help you select the right instruments for your application, set up an institutional account, or answer any technical questions about anthropometric measurement.