What more is there to say? It's something you can use to wrap your cables in before you throw it into your bag. It's a bit big compared to other cable winders, but I designed this mainly for thicker 4mm diameter cables. 

To use, stuff one end of the cable in one of the fingers if needed, there are slots for 3,4,5mm cables. Then just wrap the cable inserting them into the holder, stuffing the other end into a finger as well if you don't want to holder to move around.

No special print instructions, just remember to give it at least 3 walls for strength. Also, print in PETG so it doesn't sag under stress of the cable.

The 15mm and 25mm refers to how long the “claws” are where you stuff the wires in.