They have a free-running roller to ensure the string can run easily without any undue friction which can cause tuning issues.
2 x 5 String Maple Banjo Bridges: 1/2 inch Clifton Essex & USA Leader
UK STOCK - 2 x Guitar String Spreaders for Fretboard / Fret Work / Cleaning
Guyker Guitar Roller String Retainers(Set of 2) – String Guide, Strings Trees...
Electric Guitar Roller String Tree Retainer String Guide Chrome Black Gold
2 X Rico Alto Saxophone No 2 Reeds And 2 X Vandoren Alto 2.5 Reeds New
6 x Roller Saddles for Tune-O-Matic Guitar Bridge
