Callaham Stratocaster Tremolo Bridge, Vintage Narrow, w/Pop-In Fender-Length Arm. 2-7/32" Screw Spacing, 2-1/16" String Spacing. Read Description For Fit List. Complete Unit as Pictured. Made in the USA using premium vintage-correct materials. Complete tremolo unit, as pictured. 2-7/32 screw spacing, but 2-1/16 (American Series) string spacing. Vintage fit, modern feel! Features Callahams Enhanced Vintage block and Virtual Pop-In arm. Arm fits snugly, with no play. Hardened steel saddles (over 100 Rockwell B) - nickel plated - for great tone, great looks! 1018 cold-rolled steel block like the vintage originals for better sustain & harmonic content.