CNC precision processed for the aluminum outer barrel extension adapter: lightweight, durable, excellent finish, and high-quality.
GSI's barrel extension, serrated surface makes it less visible when barrel extensions of various lengths are extended to each other

* In the product, (-) means reverse thread and (+) means positive thread.
The threads of the outer ring, flame extinguisher, and silencer, are not marked separately; they are (-) reverse threads, and the tightening direction is counterclockwise from the front.
 
• EAN & SKU : 8809899600078, SKU:  BE21-AR20
• Product Dimension & Weight: 1.34(L)x0.68(W)x0.68(H) inch 0.3oz
• Package Weight & Dimension:  5(L)x 3.3(W) x 0.7(H) inch 0.6 oz 
• Made in Korea