storm door latches

It's hard to nail down an exact back set with surface mounted type locks like the 40-058. I would say on the approximate back set would be around 7/8". It depends on the width of the "face" on the door where the lock will be mounted, as well as the placement of the strike/keeper and where you need to install it. If you want, you can send us some photos of the lock set you need to replace on your storm door and we can make a suggestion.