sd-holder = screwdriver-holder
7X = 7 slots for screwdrivers
7X = 4-5 Screwdrivers
9X = 5-7 Screwdrivers
11X = 6-9 Screwdrivers
13X = 8-11 Screwdrivers
15X = 10-13 Screwdrivers
This is only a recommendation !!!
7X = 114mm
9X = 142mm
11X = 170mm
13X = 198mm
15X = 226mm
The author marked this model as their own original creation.