SilencerCo Thread Protector with O-Ring Engagement 1/2x28 Black. Made from stainless steel and finished in black oxide this thread protector can be a replacement to an already purchased adapter. Also if a gunsmith threads a barrel with SilencerCo's unique O-ring engagement feature this thread protector is perfect. Specifications for SilencerCo Thread Protector with O-Ring Engagement: Manufacturer: SilencerCo Color: Black Threads per Inch: 1/2x28 Condition: New Fabric/Material: Stainless Steel Package Contents: SilencerCo Thread Protector with O-Ring Engagement SilencerCo AC6: Thread Protector with O-Ring Engagement 1/2x28 Black