Various add-on gadgets strive to improve vibrato systems. An issue with nearly all vibrato systems is that bending one string can slightly drop the pitch of all the others—a problem not present on fixed-bridge instruments. One after-market tool, the Tremol-No, temporarily locks the vibrato mechanism. Two thumbscrews let a player choose between completely locked, downwards pitch only, or normal free movement. One of the guitarists who was well known for using this gadget is Guthrie Govan, who had it as a standard feature on his signature guitar models from Suhr Guitars. He has however since moved to Charvel guitars, and appears to have dropped it from his specs.