
This looks a bit dodgey to me...
LInky
If youv got a problem its just covering it up.
I spent the extra tenner and got a local garage to do it for me 
Its not a problem.....
Converted a 928 a couple of years ago from Freon to R134a, got a kit from the states, simlar to this with an extra can, some valve adaptors and
cleaner.
Gas is gas after all, you can now buy this at Halfords.
I got a huge can off of Ebay two years ago for £100, its charged 5 cars so far with plenty left so this may not be that cheap !
However being that the local man charges £60 to even have a look, as long as your system is not leaking after 5 years it probally will need a boost as
the gas eventually seeps through the hoses.
Regards Mark
Current opinion is, they're fine as long as you're just "topping up" but if the system is empty(compressot not kicking in), get it sorted by a pro.