The Tippmann Response Trigger Control Adapter O-Ring. This is also called a cross bolt O-ring. For the A5 Response Trigger, the O-ring is used in all three slots. The outer one is slightly larger, but uses the same O-ring. For the X7 Response Trigger uses it as the Flow Control Adapter O-ring.
This product is used in the following guns: X7 Response.
The Tippmann Part Number for this product is 02-84.