At Photo/Graphics we package our print orders as "Units".   You can order 1/2 units

such as single 5x7 prints, pairs of 4x6's as well as prints that take multiple units such as

the 11x14 which takes 2 units.

Size Unit
8 x 10 1   
2 - 5 x 7 1   
4 - 4 x 5* 1   
4 - 4 x 6* 1   
8 wallets 1   
5 x 7  1/2
1 - 4 x 5  1/4
1 - 4 x 6  1/4
11 x 14 2   
16 x 20 3 1/2
20 x 24 5   
20 x 30 7   
16 wallets* 1 1/2
24 wallets* 2   
48 wallets* 3   

* from the same image