This spring is following the “APS 13 mm standard” (for 9 mm outside diameter spring guide). It will fit any rifle compatible with this standard, including all SRS (except push mechanism) and all TAC-41. While being compressed at 99 mm in length, it delivers 150 Newton (+/- 5%, around 9 Kg of force). This spring received a black electrophoresis coating, and a laser marking to quickly identify the spring.