In our design of the Ultrastream we wanted to – where possible – reduce waste of materials. We really wanted a stainless steel outer sleeve for strength and cleanliness, but didn’t want to throw it away with each filter change, so we had our engineers create a removable sleeve.
It’s a tight fit, and so when you want to change over to a\\e new filter, (which comes without sleeve) you may need to put the filter with sleeve under hot water to create some expansion of the stainless steel, thus loosening it to make its removal easier.