Works, but the plastic is soft and easily torn.  The seal is good and I still use it after a year, but I've had to make minor repairs to it to keep it in one piece.  I'd pay more for the same item made of slightly better materials.  If having a working respirator is really important and you are in a hurry, I'd get a higher quality respirator.  For occasional shop use or an emergency kit, this is probably fine.