ForceFlex technology incorporates patented multi-injection molding of the lens with a flexible Thermo Plastic Urethane (TPU) frame. Due to this construction, it can achieve a military ballistic level impact resistance at over 1000 feet per second. The TPU material allows the frame to flex and fit individual faces from large to small.SEPTLS135FF124. TLS135FF124. Crews Crews ForceFlex Protective Eyewear - FF124.