The MD Silentmaster CV unit I have can use two types of woven bags-An open top one or a completely closed version.The enclosed is easier to replace.The open one is like a GIANT TriStar bag.You replace it when about half full so you can wad the upper neck of the bag over the dust.-then use like a handle to lift out of the machine.Then install a new bag.They are held in by a rubber collar at the top of the bag.The enclosed bag does not use a coller-the open bag holds like 12 gal of debris-the enclosed one about 8.