Our C & R Gear Covers are built with 1000d. Cordura®Nylon with a DWR (Durable Water Repellent) process. The urethane® coating provides a hidden barrier; water just beads off.  
And for extra protection, try our Padded Gear Cover.  We heat laminate a 1/2" polyfoam material with brush tricote (soft cloth) backing.  Have a tweed amp?  Perhaps our new Beige Padded Road Gear Cover is a perfect match.