Long enough and wide enough to comfortably hold two rolled up US standard size playmats or even a rigid plastic playmat tube.  It will even hold one of the crazy double sided mats!  It won't bend and dent and crack like a tube...or lose and end.  It's all self contained with string and grasping clasp and now with a built in carabiner.  Made with vinyl heavy fabric.  I'll sign it unless you tell me not to.

The photo has two bags to show the fill image.  This listing is for one bag.