L2D Combat Thread Protector Retainer Lo-Pro O-Rings 3-Pack Black. This is not your standard rubber O-Ring these thin lo-profile O-Rings are made of Viton ( fluorocarbon elastomer ) and can withstand temperatures from -15 degress to 450 degrees fahrenheit. The material is also resistant to cleaning solvents oils and other chemicals that will break down regular rubber O-rings. The retainer O-ring is not visbile when your thread protector is tightened into place and are perfectly sized to prevent movement. 3 O-Rings to a Pack. Specifications for L2D Combat Thread Protector Retainer Lo-Pro O-Rings 3-Pack: Manufacturer: L2D Combat Finish: Black Additional Features: 3 pack Package Contents: L2D Combat Thread Protector Retainer Lo-Pro O-Rings 3-Pack L2D Combat 3HD-FOR-TORLPOR: Thread Protector Retainer Lo-Pro O-Rings 3-Pack Black