Bass string winders. These tools can quickly and easily detune and tighten your bass strings when changing. This can be a surprisingly tedious process and uncomfortable for your hands, and these cheap tools can make the whole thing quite painless- particularly for upright bass.
Guitar Bass 3 in 1 Maintenance Tool, String Peg Winder, Strings Cut, Strings ...
Guitar Bass 3 in 1 Maintenance Tool,  String Peg Winder,  Strings Cut,  Strings ... Price: $11.64
Guitar Bass Peg String Winder Head Tool Bridges Puller Drill Hexagonal RemovePX
Guitar Bass Peg String Winder Head Tool Bridges Puller Drill Hexagonal RemovePX Price: $5.75
Multifunctional String Peg Winder for Guitars Bass Repair Luthier Tool I0N9
Multifunctional String Peg Winder for Guitars Bass Repair Luthier Tool I0N9 Price: $3.13
Black Planet Waves Guitar String Winder Cutter Guitar Bass Maintenance Tool Pro
Black Planet Waves Guitar String Winder Cutter Guitar Bass Maintenance Tool Pro Price: $2.96
Electric Guitar Bass Peg String Winder Tools Bridge Pin Puller Plastic Remover
Electric Guitar Bass Peg String Winder Tools Bridge Pin Puller Plastic Remover Price: $4.38