This aluminium spring bushing is made by precision CNC machines.  It fits Glock 17 Gen4 (T.Marui).  This enhanced spring bushing is made for professional shooter and competition needs because it has:

1.High precision dimension with light weight construction;
2.Dimension is modified for strengthen construction to improve reliability. Therefore, it has difference size from the original T.Marui bushing;
3.Aluminium construction increases durability;
4.Smooth surface finishing to reduce friction with springs;
5.Black colour hardcoating-anodized finishing.