That's an excellent price - too bad they won't ship outside the U.S. As for the difference in kits, I can't speak to that, but I've seen posts by others that stated that the two kits are identical.
The only other kit I've found is in Japan, and is a lot more expensive. But they give you the option of ordering a 7" kit or a 6.5" kit. Standard double DIN is 7 inches, so I'm not sure what the 6.5" kit would be for. The seller states that it is original OEM equipment, so perhaps it's made by Mazda in Japan.
The problem with this seller, though, is that I've read a number of poor reviews where it took months to receive the kit - and I haven't found it sold anywhere else.
I ended up buying the Metra kit (but haven't gotten it yet). Hopefully the fit won't be too bad - I'm planning on painting it black, anyway.
Here's a link to the Japanese kit, in case you're interested:
https://www.ebay.com (commissions earned)
