This air vane spring is used as part of the auto-choke system. It maintains the proper tension on the air vane choking system It works with many Toro and Lawn Boy mowers, and many other mowers like Craftsman Troy Bilt that use BS engines Easy to install with right tension and length, to bring your mower back to single-pull start To replace the part# 790849 Package including 5pcs air vane choke springs Air Vane Spring Fit for BS - Choke Spring Fit for Toro Craftsman Troy Bilt Lawn Mower, Carburator Air Spring for Mower, Replace 790849, 5pcs This air vane spring is used as part of the auto-choke system. It maintains the proper tension on the air vane choking system It works with many Toro and Lawn Boy mowers, and many other mowers like Craftsman Troy Bilt that use BS engines Easy to install with right tension and length, to bring your mower back to single-pull start To replace the part# 790849 Package including 5pcs air vane choke springs