Quad comes with 4 standard slots for mouthpieces, but that is not the end of the description. Indeed there are three spaces in between the slots for your imagination about the use. Though a bit off-label, you can store three more trumpet mouthpieces upside-down without impeding the closure. For Breslmair modular system components, the extra space is the room just right for a few unused rims/cups/backbores in a small Ziploc bag - this mouthpiece bag is indispensable.