Shopped around a bit & saw this product with a pump for an amazing price! Bit sceptical, but very impressed when it arrived.
Ok, so it comes with a photocopied sheet of exercises rather than a glossy book or DVD, but if you want that, pay the extra £30 for another product!
Does exactly what is says on the tin, needs occasional topping up with air, but has been excellent for keeping my dodgy back flexible, and helping improve core strength.
Just buy one!