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.
Practical Peg Winder+Cutter Clipper+Bridge Pin Puller Bass Guitar String Tool zx
Practical Peg Winder+Cutter Clipper+Bridge Pin Puller Bass Guitar String Tool zx Price: $2.64
Practical Peg Winder+Cutter Clipper+Bridge Pin Puller Bass Guitar String Tool cv
Practical Peg Winder+Cutter Clipper+Bridge Pin Puller Bass Guitar String Tool cv Price: $2.03
D'Addario Planet Waves Bass Guitar String Peg Winder
D'Addario Planet Waves Bass Guitar String Peg Winder Price: $6.99
10 Pack D'Addario Planet Waves Ergonomic Bass Guitar Peg Winder, PWPW1B
10 Pack D'Addario   Planet Waves Ergonomic Bass Guitar Peg Winder,  PWPW1B Price: $62.95
3 in 1 Guitar String Winder Cutter Puller for Guitar Bass Mandolin Ukulele
3 in 1 Guitar String Winder Cutter Puller for Guitar Bass Mandolin Ukulele Price: $19.46