CNC precision processed for the aluminum outer barrel extension adapter: lightweight, durable, excellent finish, and high-quality.
The 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 : 8809899600061 , SKU:  BE21-AR45
• Product Dimension & Weight: 2.30(L)x0.71(W)x0.71(H) inch 0.8 oz
• Package Weight & Dimension:  5(L)x 3.3(W) x 0.72(H) inch 1.1 oz 
• Made in Korea