Just make sure you let your insurers know - that's another forty quids worth of kit you've got in the gig bag there ;-)
Seriously though, what a shame nordstrand didn't pitch the price a little better. It's actually a cracking idea, because a lot of the other ways of doing this (including the Bassmute which I use and love) push against the strings and do cause tuning issues. This as far as I can tell doesn't, is easy to get on and off, and I'm assuming is adjustable in terms of muting depending on how far/hard you push it on?If nordy had these made in china by the thousands for 10p a throw and sold them for £5-10 not many of us would be arsed buying the foam, glue and lollipops to make them ourselves. They would become an essential part of our standard kit and they would have regular repeat business through disorganised and short sighted folk like me losing one every few months.