The SP6920CK is Colt’s latest offering at an unbeatable upgrade. The 16.1 inch barrel features a 1/7 twist, M4-profile barrel along with a charging handle and bolt carrier group. Equipped with a back-up MaTech rear iron sight, the SP6920CK comes with a conversion pivot pin to accommodate larger diameter front pivot holes in older models. Now you can convert ANY Colt rifle to the most state-of-the-art configuration.