Swing-Mate™ comfort springs feature a barrel-shaped extension spring specially designed for comfort. The spring is manufactured from .218 diameter heavy-duty music wire and heavily zinc plated for rust resistance; it is 2" in diameter and 8.5" long with a weight capacity of 600 pounds each. Two springs are great for 2' through 7' wide swings. Swing-Mate™ comfort springs are designed to fit between the ceiling hooks and the swing chain. This helps reduce the shock stress to support structures and creates a soft gliding on air affect that most people love. Swing-Mate™ comfort springs are primarily designed for use with porch swings and hammocks.