The great rubber smell of this bag is a big plus for rubber lovers. But this Rebreather Bag is mainly used with breath control play. When you exhale into the bag and then inhale that air again, the oxygen level drops. With the shut-off valve on the other side, you can set how much fresh air you let in.
Breath control play is a lot of fun, especially in combination with bondage. But safety first: solo breath play is a known killer in the kink scene. NEVER play alone. NEVER leave your partner unattended, not even for a minute.