Amazon.com: Vencetmat 4mm & 5mm Truss Rod Wrench, Allen Wrench Tool Ball End for Martin Acoustic Guitar Truss Rod Adjustment And Deep or Narrow Truss Adjustment. : Musical Instruments
4mm Allen Wrench, 75 x 55mm, 271945 — WSI Machinery
30-100pcs 0.9mm 1.27mm 1.5mm 2mm 2.5mm 3mm 4mm Black Allen Wrench (Socket Head screw Wrench) Hex Key - AliExpress
ARRI 4mm Hex Key (5/32" Allen Wrench) K2.0010434 B&H Photo Video
4mm Metric T-Handle Ball Point Hex Wrench — BoxoUSA
5010 Allen Key 4mm
Leke 4mm 5mm Ball End Guitar Truss Rod Tool Allen Wrench for Martin Acoustic Guitar - Walmart.com