Double Coil Support 1/2 "

Thanks for posting. Simonton windows, like many brands, can use a few different coil balance assemblies. It's certainly possible you might just have an older version of the 15-150D; however there's also the similar 15-204, which is meant for a 3/8" thick Coil Balance spring. To determine what you're working with, the best thing to do is to remove your assembly from the window and send us a picture of the pivot shoe. The identity of the pivot shoe determines the identity of the coil springs you need. Also, if you could measure the thickness of the coil tape, it should either be 1/2" or 3/8"; that will determine the rest. From there we'll do our best to assist you.