Not heard of those , but beware of gimmicky products umbre ,I have been looking into co2 bags that you just hang in your grow room. I have heard they work pretty well and priced pretty well. Quick, easy and cheap works for me.
I can't find a UK stockist , hmmmm , worth a try though , try doing a 2 plant comparison , 1 with , 1 without , maybe make a thread,Here is just the first link I found real quick.
http://www.amazon.com/CO2-Boost-Buddy-All-Natural/dp/B005I4CB2I
I have talked to people who have used similar and say they work great. And they have pretty large grows. I have seen them for around $30 and I will be giving it a try soon. Will let everyone know how they go.
Thanks , i may order 1 and run a test , cheeeerz Umbre... still not cheap lol!Here is another link
http://www.alternativeco2.com/CO2-Bags-s/33.htm