"The Travel sock is a large sack made of breathable fabric that the hammock hangs inside of. It’s identical to our Travel Net in design and dimensions and only differs in the fabric used. This is used mainly in cold weather to block more wind and increase inside temperature by around 15degF. It can be used with our Blackbird and Traveler series hammocks or any end-gathered hammock up to 10’ body w/101” ridgeline length.
 
Weight: 9.25 oz.
Fabric: 20D Nylon, DWR"
 
The above wording is straight from Brandon, and his team at Warbonnet Outdoors. 
 
Comes with a Stuff Sack.
 
View the full product details on the Warbonnet Outdoor website.