Putters are speed 1 to 3, midranges 4 to 5, fairways 6 to 8, and distance drivers 9 to 14. An empty band is a gap. Two discs with nearly the same speed, turn, and fade, in the same stability class, are an overlap.
A bag of only overstable discs gets a suggestion for an understable slot. A bag of only understable discs gets the opposite. The suggestion is a set of numbers, not a brand.
The first flight path is free. $5 unlocks the gap list, the suggestions, a printable bag card, and a CSV.