WRS Amesbury Block & Tackle Balance for Non-Tilt Windows - 37" 3640 (23-30 lbs)

Upgrade your windows with the strength and stability of the WRS Amesbury Series 400 Block & Tackle Balance—engineered for heavy-duty performance and long-lasting reliability.

Built for non-tilt, side-load systems, it provides precise lift control and smooth operation for heavier sashes in residential or commercial use. Combining Amesbury’s engineering with proven block-and-tackle mechanics, it ensures consistent, dependable motion.

Each balance features a reinforced pulley-and-spring system and a 5/8″ galvanized steel channel that resists rust, bending, and wear—maintaining reliable lift through thousands of cycles. Pre-assembled with non-winged guides, it installs quickly and is precision-tested for durability.

Whether replacing one or upgrading many, the Series 400 delivers the strength, precision, and performance you can trust.

Design: Non-tilt, side-load block & tackle

Selection Guide

• Measure the metal channel only — do not include the plastic ends.
• Check that the channel depth is 5/8", measured from the spring opening to the back of the balance.
• Match the stamped number to your sash weight (e.g., “910” = 10″ length / 3–6 lbs).
• Replace both balances in the same window for best results.

Important Notes

• The balance length is always 1 inch longer than the stamped number on the metal channel
• Balances 20" or longer may need special handling due to their size.
• Accessories and mounting hardware are sold separately.

Trusted for over 30 years, WRS Window Repair Systems provides precision-engineered hardware built to keep windows operating safely, smoothly, and efficiently for years to come.