Noob question, bruteforce pmkid/wpa2 ISP default passwords

hello,

I am trying to crack a wpa2/pmkid hash, using a mask or ruleset

the hash I am trying to brute has the following properties

• exactly 12 characters long
  
• only uppercase
  
• numbers 0-9
  

my questions are is rule/mask based even the way to approach this?
or should i be using something else

Thanks in advance,

Shroom