Silverback GBB type Flat hop Rubber Set

“GBB” type, flat hopup rubber, 4 hardness set (50°/60°/70°/80°) Initially designed for the TAC-41 “GBB” hopup, this hopup rubber can fit inside most of airsoft guns using “GBB” hopup rubber. Transparent silicone for easier installation, this kit includes 4 hardness: blue color, 50°, green color, 60°, yellow color, 70°, red color, 80°