Question about the front fender mudguard/extender

[Watevaman]

 I've been putting this off for a long time but I think it's time I should get one of these things. Do those of you with them (I don't know if they were factory or not) think they make a big difference to the amount of stuff thrown onto the exhaust/engine when riding in the wet or on loose material?

And also, does anyone know what size bolts/nuts are used to hold them on. I'd rather just go to a hardware store instead of paying $1.50 for a tiny bolt at the dealer.

[adidasguy]

1. Yes they help (and they look cool)

2. Whatever bolts work.  Short M5's should work. Maybe M4's.