Thread: Cross brace bolt size?

Some how I ended up losing one of the bolts for my cross brace. Does anyone know what size the bolt is so I can replace it?

thanks.

13mm is the head size....does that meant the thread size is 13mm?

I think its like a M12x1.5 on top and M10x1.5 on the bottom, take one you have to the hardware store and use a thread checker.