Brand new steel spring guide for the sniper rifles. Allows to use standard stock 7mm springs and also upgraded 9mm springs. Inner steel guide with the bearing has outer diamater 7mm and once you put 9mm rotation sleeve on it, then you can use upgrade 9mm springs. (means inner spring diameter) Outer rotation spring guide sleeve is equiped with the thrust axial bearing. It makes bull back much smoother, because allows limited spring rotation. Spring guide is suitable for APS system. For example Well MB01,04,05,06,08,13,14, or CA/SW M24. Not suitable for VSR or AWS system