The radius block is wide enough to work on guitars up to 8 strings, and basses up to 5 strings.
Guitar Neck Radius Sanding Block - Hellfire - The Sandman - Modular - 3 Lengths
Guitar Neck Radius Sanding Block - Hellfire - The Sandman
Guitar Bass Radius Sanding Block Fret Leveling Luthier Tool Fingerboard Leveler
Guitar Fretboard Radius Jig for Guitar Bass Luthiers
Guitar Fretboard Radius Gauge Set
Fretboard radius milling jig / fretboard radius jig luthier tool