For GHK AKM series GBB
● AK series, air tight o-ring, grey color.
● O-ring size (I.D.x W)：15.8x2.4 mm
● This item is the same as the part #AUG-15-4, #553-15-4
For GHK AKM series GBB
● AK series, air tight o-ring, grey color.
● O-ring size (I.D.x W)：15.8x2.4 mm
● This item is the same as the part #AUG-15-4, #553-15-4