Prime-Line 3580 Window Sash Balance, 10 Lb, 2 Cable, 6-3/8 in H X 3-1/4 in W, Steel, 10-lb 10 Pound counter balance per cable All steel construction coil spring retraction Two steel cables, one for upper sash and one for lower For replacement of existing balance or to retrofit old style pulley and weight Use either one or two balances per window, 2 each #10 balances for a 20 pound sash Verify dimensions against line drawing image before ordering