Luth-AR .223/5.56 Weld Spring Black. 223/5.56 Weld Spring (Barrel) SKU: BL-08 Specifications for Luth-AR .223/5.56 Weld Spring - Barrel: Manufacturer: Luth-AR Color: Black Finish: Anodized Fabric/Material: Stainless Steel Steel Caliber: 5.56x45mm NATO .223 Remington Gun Make: AR Platform Gun Model: AR-15 Features of Luth-AR .223/5.56 Weld Spring - Barrel: Shipping Weight .5 lbs Shipping Dimensions 3 x 3 x .5 in Package Contents: Luth-AR .223/5.56 Weld Spring - Barrel What firearm models does the manufacturer say Luth-AR .223/5.56 Weld Spring - Barrel is compatible with? The manufacturer says that Luth-AR .223/5.56 Weld Spring - Barrel is compatible with AR-15Luth-AR BL-08: .223/5.56 Weld Spring Black