These screws are replacement rivets for our Illumiflaps. The only tools needed are a flat-head screwdriver and some Red Loctite to keep them secured. They are sold as a single rivet (Chicago screw with post), please order multiple if you are in need of more than one replacement. 
 
To determine which size you need, please refer to the thickness of your mud flap, 3/16in. and 1/4in with full rigid plastic back, 5/16in. rubber back, or 1/2in. rubber back. These measurements are the total thickness of the mud flap. If you are unsure of which size you need please send us an email with a picture of the side of your mud flap and your order number and information. Please send emails to frigidnorthcustoms@gmail.com