SilencerCo Delta Adapter 1/2x28 Black. Available in multiple models enjoy the benefits of o-ring engagement which keep the muzzle threads clean and prevent your suppressor from working loose under firing. Models: 1/2 X 28 TO 1/2 X 28 O-RING ENGAGEMENT ADAPTER (AC3) 1/2 X 20 TO 1/2 X 28 (AC115) Specifications for SilencerCo Delta 1/2x28 Adapter: Manufacturer: SilencerCo Fabric/Material: Steel Color: Black Condition: New Package Contents: SilencerCo Delta 1/2x28 Adapter SilencerCo AC3: Delta Adapter 1/2x28 Black