VANSON 5mm Chrome Screw-In Tremolo Arm / Whammy Bar for Fender Mexican / USA Stratocasters

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£5.70 GBP

VANSON 5mm threaded Chrome Tremolo Arm.

Arm Diameter M5 (thread diameter in reality approx 4.80mm)

As a rule of thumb here's a good sizing reference, duly credited to 'CeltRocka' on;
All USA strats: 10-32 UNF [equivalent 4.82mm]
All Made in Mexico and Made in Japan: M5 [4.80mm thread]
Squier Classic Vibe and Affinity- M5 [4.80mm thread]
Squier Bullets, Deluxes and Standards are usually M6 [5.80mm thread]  but sometimes 10-24UNC (M5)
Generic Imports Brands are often M6 [5.80mm thread]

If you are unsure you can always try an M5 or M6 bolt from a hardware store first, to check the thread of your tremolo/vibrato unit.