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I have been using the N2 in my HS Envoy without a problem. As others have said they are identical except for color and the method of holding them in the spa. The HS holds with an over-sized ring from the top and the N2 with a stick from the bottom. As an experiment I have removed the ring from the HS filter and used it on the N2 but it's easier to use the sticks. The Envoy works with just one of the sticks.