Heavy canvas. Nice, heavy brass zipper. Good stitching. Pleasantly surprised at the quality. My only dislike is that the sewn-in 'pockets' on the inside are too small of much use. They're big enough to put your index finger in and that's it. Some folks may find them useful. I didn't. It's ok though, I didn't buy the bag with intentions of using them anyways. Great product. I will probably buy more for other tools I own. Thank you.