The Seals Neoprene Cockpit Cover is 4mm neoprene with  3/8" stitched bungee. Tether hook. The most secure cockpit cover for your kayak, ideal for car topping or keeping critters and debris out of your kayak. Neoprene covers reduce puddling and fit more taut than nylon or vinyl covers, but are not necessarily more difficult to put on.  If you need the most durable protection from sun and salt check out Seals Cockpit Seal. Cockpit Seal Ultra  packs down the smallest if space considerations are most important.
 
Pictured is a size 1.7 on a Delta Kayaks 12.10. 
 
Size 1.4 fits Delta Kayaks 12s & 15s
Size 1.7 fits Delta Kayaks 12.10, 14, 15.5GT, 16, 17 & 17.5T