Size: -86x30x4mm
(length between the bolts is 58mm)

Bolts and nuts: 2x M4, length depends on the keys. 

Gauge: M3-M6 with the most used lengths 6mm-40mm

Adjust the tightness with the bolts and the keys can be flipped off, or make it loose and the keys will be wobbly.

Use for even-numbered keys, otherwise it must be spaced or placed all keys to one side.

It can be expanded, depends on the lenght of the bolts.