Motorcycle & Scooter covers generally fall in one of three groups:

• Lightweight travel covers pack extremely compact, may have some level of water resistance, and are mostly used to protect a motorcycle from harmful UV light, tree saps, and other debris.
• Full protective covers have much heavier construction, are usually too bulky for travel, are 100% waterproof/vented, and will protect the entire bike from the elements or prying eyes. These are best for every day / all day use.
• Indoor or dust covers have no waterproofing, but therefore have no condensation issues either.

Lifetime Warranty. Many heavy duty covers come with a manufacturers Limited Lifetime Warranty. Keep in mind that deterioration from harsh elements is usually not covered under warranty. But think about the harm prevented to your bike, you want the cover to take the beating instead of your bike.