Unlike other tuners which require countersinking of the holes in the head-stock to accommodate protrusions around the shafts, the baseplates of the Rubners are flat and the 6mm shafts come straight out of the baseplate and require only a 1/4" (6.4mm) hole for each shaft. This makes installation easier and less likely to weaken the head-stock.

What we really like about Rubner machine heads is that even the lowest priced sets look nice and work well, they don't look cheap like other brands in the price range. Price is based on the level of engraving on the baseplates, the materials used for the button.

REPLACING SLOTTED-HEAD ACOUSTIC GUITAR TUNERS
It's unlikely you will find an exact replacement set for most guitars, especially for older guitars. In this case just choose a set which looks like it will suit the guitar and cover the original screw holes.

Most acoustic guitars with slotted headstocks have a standard 35mm (1-3/8") roller spacing centre-to-centre. Some guitars use other spacings. If your guitar has a different spacing you will need to use single tuners, or have a set custom made.

The screw holes often will not line up. If this is the case you can usually drill new holes without any issues. If a hole overlaps but doesn't line up with the new set you will need to fill it and drill a new hole in the correct place.