Prime-Line products has been supplying repair and replacement parts for windows and doors. These extension springs from Prime-Line are constructed from 0.072-gauge, heat-tempered, spring steel wire plated in a bright nickel finish. They offer superior strength and long lasting tension. These springs feature a single loop, open-ended design. This type of spring can be used on toys, equipment, tools and for a variety of other household.. See full description for further details