Mine is a soft, rain-proof, light gray fabric. It's a 'generic' size but shaped for an 18' center console and also covers the engine. I pull it down to the trailer with shock cords, but it isn't tight enough to tow. But it does keep the boat clean/dry inside. I have found that the generic covers need some sort of support under them aft of the console...otherwise they pool water. I glued up a very simple "bridge" - it's essentially two Indian bows (think: Bow and Arrow) of pvc (1" dia.). They are held in the 'bow' shape by cord stretched from one end to the other. The parallel bows are joined in two places with 24" long tees/pvc. I capped the ends and they just rest on the gunwales.
I like the fabric because it's soft enough to go right into the washing machine.
I think I paid about $100 for the cover...