the turbines -come in packs of 3 and cost around $15 for a starter pack - then about $30 for a pack of 3 the same size. The mute i think will be similar. They should last a month then you need to REPLACE it!!! - thas what i like, and if its working and your wife is getting a good nights sleep then its off to boots for a otc 10 quid purchase. This is a winner