The Eson 2 diffuser has taken over from the popularity of the Eson diffuser. The diffuser is a new washable version and will last a lot longer than the previous disposable diffusers. The purpose of the diffuser is to diffuse air from the front of the mask and in doing so prevents air hitting your partner through the night. This also acts to reduce the noise form the exhalation ports. The use of the diffuser is purely optional but once you use it you will want to continue.
When washing simply user warm soapy water and make sure it air dries before using.
One size fits all however this cannot be used on the previous Eson due to connectivity.