3+3, nickel, 90°, kidney button. Drill hole 10mm. Highest possible tuning stability! After the string is put through the horizontal hole of the shaft and is placed tightly over the frets you tighten the wheel on the backside counterclockwise. When doing this a small pin inside the shaft is tightening the string in the hole. After having done this you can start tuning. And our backlock tuners have a genious point: when turning back the locking wheel you finally end up in an open loop so that the wheel cannot fall off and never can get lost!