1. For martin or other guitar which couldn't reach it with a regular hex wrench truss rod adjustment. 2. Two way L-shape truss rod adjustment tool. 3. Made of carbon steel, durable and highly wear-resistant. 4. Set for most kinds of acoustic guitar, electric guitar and bass. 5. For locking hexagonal screws on the bridge, adjusting the guitar neck. Weight: Approx. 42-66g / 1.5-2.3oz Length: Approx. 75+126mm / 3.0+5.0in Diameter: Approx. 4 or 5mm / 0.2in Optional Type: 4mm/5mm size:70x120mm Material:Carbon steel colour:Black Package Contents: 1 x 4mm wrench 1 x 5mm wrench Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.