1 1/16, but I used channel locks, took that bracket out of the way (right in front of it, with the ground wire to it), popped it right out. Head up Lowes or Home depot, visit the plumbing section, you can make a rig to keep the stock sending unit in there also, you won't have a dead gage in the cluster. Good luck
If you try channel locks or vice grips, make sure they're sharp (ie new)