Battery you need - https://amzn.to/2YuDne3

Here is a quick little video of me showing you how to replace the battery on a Mazda 3 and Mazda 6 Key fob. This fob covers the years 2004-20068 Hope it was helpful!

Part number P/N : KPU41794

This remote also fits:

07 08 Mazda 3
03 04 05 Mazda 6 hatchback