M_Boats: Questions on M15 rigging – Bent bolt

I was out sailing on my M15 Saturday and noticed that the bolt that attaches the shrouds and forestay to the top of the mast is bent. I’m going to replace it, but first I need some advice. I assume it is ¼ inch stainless, but do I need to buy a special grade bolt? There is a West Marine store nearby so I’m guessing they will have what I need. Just need to know what to ask for. I’m kind of wondering how this could happen. The rigging is properly tensioned and when I stand the mast I attach the forestay by hand. Has anyone noticed the same thing on his or her rigging? Hank Kant