Jaeger Precision shows how one owners of the Silverback Tac-41 can install the GBB type Hop-Up unit. The TAC-41 optional hopup unit is designed for use with "GBB" (Gas Blow Back) style inner barrels and hopup rubbers. It's made from high-quality CNC machined parts and includes a feeding system to prevent double feeding. This unit is compatible with most "GBB" type components and allows for some adjustment of the inner barrel for different brands.  However, it requires a specific optional cylinder head (SBA-CYL-33) to function and inner barrels at least 3mm shorter than those used with the standard TAC-41 hopup unit. There's also a compatible advanced hop up kit (SBA-HOP-34) available for further customization.