These are new production knobs from the same company that originally made the knobs for Sunn and Music Man amps in the 60s, 70s, and 80s. They are the same dimensions as the original knobs, and only .5 grams lighter due to a different, lower-mass plastic being used. 1/4" (6.35 mm) bushing with cylindrical set screw, so they will fit on original, American-made 1/4" shaft pots, as well as later production 6 mm, foreign-made pots. 

Material is slightly glossier than older knobs, due to not being scuffed by 40+ years of handling. The chief distinction between these and "Fender-style" knobs is that they are numbered 0-10 instead of 1-10. 

Many Sunn and Music Man amps have had their knobs partially or entirely replaced with Fender 1-10 knobs, so these would aid in restoring it to the original look. Additionally, modern Fender reproduction "Sunn' Model T amps were fitted with 1-10 Fender knobs so these would give those amps a more vintage-appropriate look.