USED JMac Customs ST-6 Skeletonized Tube 6in Black ST-6. (With proper folding adapter) Requires a mount or folding mech to install Specifications for JMac Customs ST-6 Skeletonized Tube: Manufacturer: JMac Customs Gun Model: M4 Stock/Brace Material: 7075 T6 Aluminum Color: Black Length: 6 in Features of JMac Customs ST-6 Skeletonized Tube Fits most M4 style stocks/braces Lightweight and Rigid Integrated QD Sling Sockers Compatible with SIG folding mechanisms Package Contents: JMac Customs ST-6 Skeletonized Tube What firearm models does the manufacturer say JMac Customs ST-6 Skeletonized Tube is compatible with? The manufacturer says that JMac Customs ST-6 Skeletonized Tube is compatible with M4JMac Customs ST-6: ST-6 Skeletonized Tube 6in Black