I need to replace a broken counter weight I need to know replacement.

See our S380-27 or S385-27. The only difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement, so compare both with your old hardware to see what matches best. For a stamp option choose 2640. 

Comparison of the S378, S380 and S385 balance shoes.