Shocktube Opinions / Advice

I was looking at a Shocktube

http://www.shocktube.co.uk

Seem decent enough and was wondering if anyone had any opinions or experiences of them?

Seem like a pretty good way to keep muck and grime off the rear shock?

Any reasons why they shouldn't be used, and are they ok to be using with esa?

Cheers.

My Mudsling keeps the shock clean and I can see if anything untoward is going on.
A cheap solution would be some wetsuit material. Hook type Velcro sticks nicely to the fabric furry side so minimal sewing needed.