tow hook

One of the two huge bolts holding my tow hook things under the back of my car has rusted off. I need to get a new bolt, but I don't know the right size/thread size? Does anyone know the dimensions?

Hey guys sadly my corolla goes back in 2 weeks so all my mods had to go. I have a bunch of mods I have no use for. Borla Rear exhaust Tein coil-overs Megan racing strut tower brace MGP caliper covers (I know not "Performance" but they look cool) Tow Hook and Adapter Bracket (rare) I'm not...