These are tools that are the essential sizes for working on Radio Control model cars and trucks. The tools are all metric sizes developed by MIP (Moore's Ideal Products). The holders were created for Jenny's RC (JRC) to organize tools at workstations and provide easy access. They would also be very handy for hobbyists at their workbench or at a track pit-stop.  Some of the older MIP tools (Gen1) and other lesser used models (i.e. ball tip wrenches) have a variety of different handle sizes. These holders are sized for the newer generation essential tools.