This conversion kit will allow you to turn your .22 K1 into a .25 caliber airgun, or vice-versa! You might not need another K1, or it might be out of reach, but this option will allow you to cover all of Huben's calibers! It has everything you need- it includes our proprietary barrel, which is made for both calibers for the K1, the magazine, and the shroud! This kit will make your K1 extremely versatile, being able to switch between calibers at need/desire!