400 Day Clock Mainsprings - Select Size Required Below

400 Day Mainspring - Select Size Below.

400 day mainsprings are made of the finest grade steel, tempered evenly throughout the entire length. They are designed to provide the right amount of power for your 400 day clock. Each mainspring is coiled to a diameter small enough to slide into the barrel easily. No expensive mainspring winder needed! Our mainsprings are sized by the width of the spring and the inside diameter of the barrel in millimeters.