Fits my 2001 JCM 2000 DSL Head like a glove.
There is no slack or too tight fitting areas, its literally perfect.
It may be perhaps pricey for what it does, but I will honestrly say that seeing the Marshall logo when my amp is cover is really cool, much nicer then just a plain surface.
It will defenitively protect your amp from dust, excessive humidity and scratches and so on, but if you are doing a lot of travelling you should consider something with actual cushion or a case.