Steel spring guide is designed for APS/L96/Type96 system sniper rifles. It means for example CA M24, SW M24, Well MB01,04,05,06,08..etc. Not suitable for VSR system or Marui AWS system (China copy Well MA4401,2) Steel body treated with zinc for the best durability. Bevel edges for better spring guide stopper insert. Outer diameter is 7mm and fit in all common springs. Axial bearing included. Please not that outer diameter of this bearing is 13mm and it must fit into piston. If not, remove it fron the spring guide.