This is quite expensive for a Thomann product, I must say. Not their usual "how can they sell these things so cheap?" bargain price which I've grown accustomed to.
To be fair, it fits the Harley Benton amp snugly even though it's half an inch too long so when you put it over the amp the cover reaches the floor before it's reached the top of the amp. Aside from that, it fits fine.
My gripe however is that it's just a very basic thin cover with no padding to it whatsoever. Only really useful as a rain cover for when you're carrying the amp from the car to the gig, or if you want it as a dust cover then I guess it'd be perfect for that - if dust is indeed a problem for you.
For the price though, I'd expect some padding as it's not actually very big - the amp itself is quite small - so there's hardly any material needed to cover it. Considering the actual amp (at time of writing) only cost £130, I fail to see how they can justify £22 for this cover. (that's 17% of the cost of the amp!) And the amp itself is outstanding and a real bargain. It's a shame that this is not.
If this wasn't part of a Christmas present I bought for my son I wouldn't personally have kept this. If you're looking for a cover to protect your amp when gigging then there are plenty of places online that will make a padded one to your specifications for around £30.
If however you're just looking for a relatively expensive dust cover, then this will certainly keep the dust at bay, but so will a tea towel...