Hi Benny - I use the Ultra Tyre Guard from Camping World. They are bungee cord attached and won't blow anywhere.
As to size, measure your tires diameter. They will NOT stretch, so if it is tight, I'd go with the next larger size.
You really can't put a cover on an INSIDE dual. If you have a tag axle you need 3 pair of covers. If not, 2 will be what you're looking for.
Mark & Sheila Heilman & The 3 Fur-Ball Princesses - Nikko, Mai-Thai & Andy
'07 MADP 4523, 2012 GMC Terrain SLT 2 wd
Blue Ox Alladin Tow Bar, M&G Engineering Dinghy Braking System