Class Code 4691
Orthotic Or Prosthetic Device Mfg
Class 4691 covers California employers who fabricate orthotic and prosthetic devices — from custom sockets and braces to assembled prosthetic components. The approved pure premium rate for September 1, 2026 is $1.907 per $100 of payroll, which is the WCIRB's base loss cost for this specialty manufacturing work.
What Class Code 4691 Covers
This classification applies to shops and laboratories that manufacture, modify or assemble orthoses and prostheses. Typical operations include taking casts and measurements, model making, thermoforming and vacuum forming of thermoplastics, composite lay-up and curing (carbon fiber/laminate), trimming and finishing with grinders and hand tools, CNC milling and 3D printing of sockets or components, mechanical assembly of modular prosthetic parts, and bench fitting/adjustment prior to clinical delivery. It covers both custom one-off fabrication and small-batch production where employees perform hands-on benchwork, tooling, assembly and testing rather than primarily providing clinical patient care.
Who It Applies To
- Independent orthotic/prosthetic fabrication labs
- In-house orthotics/prosthetics workshops at hospitals or clinics that perform fabrication
- Small medical device manufacturers focused on custom prosthetic components
- Orthotic/prosthetic technicians and fabrication bench staff
- CNC operators and additive manufacturing (3D printing) technicians working on sockets and fittings
Common Job Duties
- Taking casts and digital scans, creating positive models and patterns
- Thermoforming, vacuum forming and trimming thermoplastic orthoses
- Composite lay-up, resin application and curing for laminated sockets
- CNC milling, finishing and post-processing of 3D-printed parts
- Mechanical assembly, alignment, adjustment and bench testing of prosthetic components
- Sanding, grinding, polishing and applying adhesives or defensive coatings
Common Injury Risks
Understanding the $1.907 Rate
The pure premium rate of $1.907 per $100 of payroll represents the WCIRB's estimated loss cost for this class; multiply your payroll for employees in Class 4691 by 0.01907 to get the pure loss cost. Insurers then add expense loads, profit margins and may apply your experience modification, payroll audits, and any credits or debits to determine the final premium your company pays.
Cal/OSHA Compliance Requirements
Fabrication shops must follow Cal/OSHA requirements for hazardous substances and machine safety: maintain a written Hazard Communication program, control airborne contaminants with local exhaust ventilation and a respiratory protection program where needed, and implement machine guarding and lockout/tagout for powered equipment. Training, fit-testing for respirators, hearing conservation where noise levels exceed limits, and documented safety procedures are also required to stay compliant and reduce exposure risks.
How Key HR Helps Employers Under Class Code 4691
A PEO like Key HR can help employers in Class 4691 by ensuring payroll is correctly allocated to the proper class code, administering claims and return-to-work programs to reduce indemnity costs, and providing targeted loss-control services — ventilation reviews, machine-guarding audits, and written safety programs. Key HR also offers training templates, OSHA compliance support and pooled purchasing power that can lower insurance expense and help improve your experience modification over time.
Get a QuoteFrequently Asked Questions
If my clinic both fits patients and fabricates devices, do we still use Class 4691?
If the primary activity is hands-on fabrication, bench work and assembly of orthotic/prosthetic devices, those payroll hours are generally reported to Class 4691. Payroll for staff whose work is primarily clinical patient care and fitting may fall under a different medical or clinical class; mixed operations often require payroll splits so each activity is classified correctly.
What practical controls most reduce injuries in an orthotic/prosthetic shop?
Key controls include local exhaust ventilation for dust/resin fumes, strict use of appropriate respirators and gloves, machine guards and push blocks for grinders and saws, anti-vibration tools or rests, adjustable benches to limit awkward postures, and routine PPE and safety training for bench staff.
How can we lower our workers' comp premium for this class?
Focus on lowering claims frequency and severity: implement documented safety programs, early-reporting and light-duty return-to-work plans, regular equipment maintenance, targeted training, and work-method improvements to reduce repetitive strain. Partnering with a PEO like Key HR can improve claims handling, accurate payroll classification, and access to safety resources that lower your experience modification and overall premium.
Quick Facts
- Class Code
- 4691
- Classification
- Orthotic Or Prosthetic Device Mfg
- Pure Premium Rate
- $1.907 / $100 payroll
- Effective Date
- September 1, 2026
- Source
- WCIRB Approved Filing
Manage Workers' Comp Through a PEO
Key HR provides pay-as-you-go workers' comp for California employers — no large deposits, no audits, better rates.
Get a Quoteor call (800) 922-4133Ready to Simplify Workers' Comp for Class Code 4691?
Key HR provides California employers with pay-as-you-go workers' comp, HR compliance support, and payroll — all through one PEO partnership.