JMac Customs Skeleton Stock 8'' w/ Rise Black. 5 (not assembled)This M4 tube adapter replaces the standard buffer tube to ensure the stock folds as flat as possibleFits most M4 style stocks/bracesLightweight and RigidIntegrated QD Sling Sockers.This version of the SM stock/brace adapter is specifically made for 4.5mm pin folding stocks. 4.5mm trunnions can be found in the SLR 104/106/107 UR/CR/FR. This stock adapter like the rest of the SM line will allow you to install all of our Arm Bar and Stocks as well as SIG style stocks. Cheek wield is adjustable by moving the stock/brace up or down on the adapter.2 height positions. Attaching a stock to a pistol makes it an SBR and requires NFA approval. Specifications for JMac Customs SS-8RP Skeleton Stock 8'' w/ Rise: Manufacturer: JMac Customs Gun Type: Rifle Color: Black Length: 8 in Weight: 6.51 oz Condition: New Stock/Brace Material: 7075 T6 Aluminum Fabric/Material: 7075-T6 Aluminum Features of JMac Customs SS-8RP Skeleton Stock 8'' w/ Rise 6'' Stock/Brace Package Contents: JMac Customs SS-8RP Skeleton Stock 8'' w/ Rise JMac Customs SS-8RP: SS-8RP Skeleton Stock 8'' w/ Rise Black