I've had this mute for about a year now, after upgrading from the practice mute by Denis Wick. It is great. The difference with the Wick mute is impressive : It is VERY quiet and has very little air resistance.
It is also much lighter : I use it everyday, the weight is crucial for me. The trombone is still of course slightly off-balanced, but not by much. I can play for 1 hour with it before feeling some effort on the left arm.
However it is still quite large and do not fit into the case. These are home mutes, not made for travel.
The only "issue" for me is that any note above a high F (the one just above the bars) is quite sharp, so it makes it difficult for me to train on high notes. But this is a common issue with all mutes.
Rating: [5 of 5 Stars!]