LIGHTWEIGHT SINGLE-COIL DESIGN: Designed for tilt-style single-hung and double-hung windows, the WRS Series 37 QuickTilt Single Coil delivers precise counterbalance and smooth sash travel. This product is sold as a set and includes one Left Hand and one Right Hand #10 coil. Each coil is rated to support 19–20.99 lb sashes, ensuring proper lift and stable operation when installed as a pair. The compact constant-force design delivers quiet, friction-free window movement. CONSTANT FORCE SPRING TECHNOLOGY: This coil spring balance uses a constant-force mechanism that maintains steady tension throughout sash travel—no pulleys or cords to wear out. The result is smooth, consistent window operation and extended component lifespan. DURABLE AAMA CLASS 3 QUALITY: Built from galvanized steel for corrosion resistance and long-term strength, each QuickTilt balance is AAMA Class 3 verified and precision-tested through thousands of open-close cycles. Coil housing measures 1-9/32″ wide with a 17/32″ coil spring for a precise, reliable fit. PRE-ASSEMBLED FOR EASY INSTALLATION: Arrives ready to install with the coil and pivot shoe pre-assembled, fitting directly into standard tilt window tracks. Designed for DIY or professional repairs, it offers fast, accurate setup and long-term dependability. TRUSTED SINCE 1989: WRS Window Repair Systems has over 30 years of experience supplying reliable, high-quality hardware. Trusted nationwide by homeowners, contractors, schools, and property managers for dependable repairs and long-lasting performance. The 37 Series is a standard coil spring window balance. This balance is designed for residential window applications. These balances feature a 17/32" coil spring in single, tandem, or triple case applications. These balance weights are evenly divided. For example, if your sash weighs 20lbs, you would need one 10lb balance on each side of your sash.