Code: I got this unused barrel extension given to me in a trade. Unknown manufacturer. No pin. I accept Gunpal(+3.5%) Asking $15 or trade for new mid-length gas tube, low-profile gas block(+$ from me), carry handle scope mount, panther grip(+$ on my end), cav arms color grips. Or box of ammo in 308, 223, 40 or 9mm(+a few bucks if any difference).