This High Temp O-Ring is made from Silicone which can stand temps of 450 degrees. Will fit around the Cocking Tube without any trouble. Each HK MP5 SD O-Ring is the sealing gasket that seals the SD suppressor against the trunion on factory HK MP5 SD’s or factory correct conversions. This is a typical wear item as they do degrade & crack with time and use. If you want to have the best suppression and operation of the SD this is a MUST HAVE spare part. This is a replacement and wear part as suggested by HK. Get a few spares to have on hand.

• MP5 SD Fits all MP5 SD models
• MP5 SD conversions using the factory sealing ring