Acoustic guitar truss rods need adjustment just like electrics, but manufacturers sure don't make it easy. Access is typically through the sound hole, and the nut may be one or two braces away. The GrooveTech Soundhole Truss Rod Wrench allows access to nuts on most makes and models of acoustics with a precision ball-end tip for easy fit, extra length on both segments of the blade, and an oversized handle for confidence when making adjustments.
Please Note - Martin guitars post-2007 (except the Modern Deluxe series) require the 5mm wrench, and most other brands will require the 4mm wrench. If in doubt, get in touch and we can tell you which size suits your guitar.