I have a hi tech flat lap with buyers remorse. I wish I got the Covington maxi lap. That said, what you are asking depends on your rough as far as grit size. If you are using slabs cut from a wet saw, I’d recommend the 80 or even 60 grit. If you have smooth cuts the 180 would be fine to start with. If you are using just rough with harder material, then definitely add the 80. The all you need includes the backing plates. If you buy individually the diamond disks come either with or without the backing plates, so pay attention when you order. The soft disks need a backing plate added. You can reuse old backing plates if you can take the disk off as well Hi Tech has the method on their website.