The main purpose of a rosin bag is to keep your rosin from having spills in your gear bag thus creating a big mess. 

This rosin bag is very high quality, extremely durable, and made out of a 1000 denier ballistic nylon material that provides resilient waterproofing to protect your rosin. Also has a heavy duty Velcro top to assure spillage is unlikely. 

The dimensions of the Rosin Bag are 6" wide by 8" tall.