Luth-AR M4 Buttstock w/Rear Sling Swivel and Mil-Spec .223 Kit Black Carbine. 223/5.56 AR lower. The kit includes an M4 Waffle Buttstock . Comes complete with Mil-Spec 6-position carbine Buffer Tube .223/5.56 Buffer Buffer Spring Latch Plate and Lock Ring. Specifications for Luth-AR M4 Buttstock w/Rear Sling Swivel and Mil-Spec .223 Kit: Manufacturer: Luth-AR Color: Black Gun Model: AR-15 Gun Type: Rifle Package Contents: Luth-AR M4 Buttstock w/Rear Sling Swivel and Mil-Spec .223 Kit M4 Waffle Buttstock Carbine 6-Position Mil-Spec Buffer Tube .223/5.56 Carbine Buffer Spring .223/5.56 buffer body 3.2 oz Latch Plate Lock Ring What firearm models does the manufacturer say Luth-AR M4 Buttstock w/Rear Sling Swivel and Mil-Spec .223 Kit is compatible with? The manufacturer says that Luth-AR M4 Buttstock w/Rear Sling Swivel and Mil-Spec .223 Kit is compatible with AR-15Luth-AR BS-M4K-M: M4 Buttstock w/Rear Sling Swivel and Mil-Spec .223 Kit Black Carbine