model #6/4 this dove to weaver super low adapter has a spring loaded mechanism to fit "under" any weaver / picatinny scope rings or accessory mount (eg dot sight), then fit to the dovetail rail and tighten screws on the rings/accessory mount which will secure the whole lot to the dovetail rail. (this is one rail). Black alloy dovetail base adjusts from 11-14mm 20-23mm weaver top 45mm long 4mm profile height + 1 slot and 9 slot option listed separately.