The wrench is sturdy and has has tuning wings to make it easier to use.
Two Headed Banjo Head Key- Grover Dual-Banjo Head Bracket
The dual banjo bracket wrench, for installing and tightening banjo heads.
This dual bracket wrench for banjo is perfect for banjo players that need both common sizes of banjo head tightening keys, 1/4 and 5/16. The vast majority of banjos are one of these two sizes. The standard "mastertone" style heavier banjos take the 1/4 while most openbacks and lesser priced "beginner" banjos take the 5/16. If you're not sure this is perfect too.
Its low cost and will cover you either way.
Both popular sizes are affixed to one key.
Two sizes 1/4" and 5/16"