This is about one new transponder key, with the chip included inside the key's head, tested and ready to be programmed.

You will need to take your actual working key with this new item to a professional locksmith  or the dealership to get it cut to fit your car's locks.
Once you have the key cut, you'll need to get it programmed to your car.

That could be done by yourself. With the item you'll receive the programming instructions. Is a very easy procedure you can follow step by step. All you need to have is two original factory working keys to do it.
If you don't have two original working keys, you will need get this new key programmed at dealer or professional locksmith. 

Keep in mind that once you get this new key programmed, you'll be able to use it with your old working key to program more keys yourself.

It fits:

(2001-2004) Mazda B2300

(2001-2004) Mazda B2500

(2001-2004) Mazda B3000

(2001-2004) Mazda B4000