Wanted to buy these, purely just because of the looks. So I really didn't expect anything, and was quite right. The sound has weird resonances at higher frequencies.
With acoustic drums, these work, if you can monitor your sound into these cans, otherwise they just damp the high frequencies (really bad for your playing balance).
If you have to do sessions, these will work OK, but the isolation isn't too great, so I wouldn't practise with these long term, SPL exposure might go beyond harmful, if longer periods of time used.