The USW-G20 conversion kit is the ultimate add on for the Glock 20 and 21 and other models in 10 mm or .45. It offers the operator the choice of using the pistol in the traditional way as well as with the built in folding stock, while the transition only requires less than a mere second. Due to its elaborated design, the operator can use the optionally available red dot sight and the original open sights as back up.The USW-G20 conversion kit fits all Glock pistols with a standard rail (Gen. 3 - 5) in calibers 10 mm Auto and .45. Red dot sight (MOS) may not be mounted.