The quick change system base plate is adaptable to all previous Ultramounts, so if you already have an Ultramount (9 5/8 tall standard, 6" JR or the 4" micro) you can convert it to a quick change mount just by purchasing this base plate and the whichever top plates you require. With the Quick Change System swapping out presses/tools takes less than 30 seconds and requires no tools. Fits: Inline Ultramount (Standard, 6" Jr, 4" Micro)