Garage door springs come in two main types: torsion springs and extension springs. Torsion springs are mounted above the door opening and use a winding mechanism to store energy. Extension springs are mounted on either side of the door and extend when the door is opened, creating tension.

The size of the garage door spring you need depends on the weight of your door and the type of spring you are using. Torsion springs are typically sized by weight, while extension springs are sized by length. You can consult a garage door professional or refer to the manufacturer's recommendations to determine the correct size spring for your application.

Garage door springs typically last for several years, but their lifespan can vary depending on factors such as frequency of use, environmental conditions, and maintenance. It is generally recommended to have your garage door springs inspected and replaced every 7-10 years.

Replacing garage door springs can be a complex and dangerous task. It is not recommended for individuals without proper training and experience to attempt this repair. Garage door springs are under high tension and can cause serious injury if not handled correctly.