This is an unused gray Premium Weathershield HP cover for a 2015-2017 Subaru Legacy from the-cover-store.com. About this type of cover they say:

Covercraft's WeatherShield HP covers are created using a unique formula to provide superior paint protection, durability, and strength. WeatherShield HP covers are ideal for long-term outdoor use.

They rate it 5/5 for water resistance and durability, and 4/5 for UV resistance. 

It has:

    • Custom mirror pockets for all over vehicle protection
    • Urethane elastic hem provides a custom fit look
    • Reinforced grommets for additional security
    • Double needle stitching providing lasting durability

It will cost you $422 if you buy it from the cover store today, so the price is a bargain. 

From the-cover-store.com you can purchase accessories if you want them:

    • Vehicle cover cable lock kit secures the cover to the car with a padlock.
    • 24" car cover storage bag
    • Cover clamps, which uses clamps and bungees to keep the cover from blowing in the wind.

More information about the cover:

Covercraft's High-Performance Material
Lightweight yet still durable, Covercraft's WeatherShield HP covers are ideal for areas with extreme rainfall and snowfall, extreme direct sunlight, moderate to heavy humidity, and moderate wind gusts.

All-Weather Protection
From freezing rain and snowstorms to harsh sunlight and bird droppings, your vehicle faces it all. Spring brings bouts of rain followed by showers of pollen, leaving your vehicle a yellow, sticky mess. Covercraft's WeatherShield HP vehicle covers are designed to provide durable, lightweight protection against anything nature throws your way. These covers are breathable, meaning heat and moisture beneath the cover quickly escapes. On top of that, WeatherShield HP covers have a nearly instant dry time after rainstorms or a stray sprinkler. If you live in an area facing extreme weather conditions year-round, investing in a Covercraft WeatherShield HP cover will keep your vehicle safe.

Details That Matter
Covercraft's WeatherShield HP covers are among the best for outdoor protection against sun, rain, and snow. These covers were developed in a parternship with Nextec Applications Inc., an industry-leader in outdoor fabrics. By using an encapsulation formula, WeatherShield HP covers provide superior paint finish protection without sacrificing strength. Features include durable double-stitched seams, an elastic front and rear hem, and reinforced non-scratch grommets for use with an optional theft-resistant cable lock. Perfect for outdoor or indoor use, Covercraft's WeatherShield HP vehicle covers will keep your investments in mint condition for years.