Anybody know what digit of the serial number will tell me if I have heavy duty brakes?

 

Isnt the heavy duty brakes a larger diameter?

 

You would think. But when I bought my rear brakes their was only one size available. Now trying to buy front brakes they want to know if they are heavy duty. I'm considering the brake job for 3 reasons.
1. Autozone has the calipers complete with slide bolts for $18
2. I took the right front caliper off one time and the clip holding the brake pad fell off and it was a nightmare getting it back on without the clip
3. Left front wheel bearings are a little sloppy.
I have a $25 autozone gift card to spend but I can only use it on their website.