By figuring out all the possible assemblies of a structure, using a mix of 2 x 6 in (152 mm), 2 x 8 in (203 mm), 2 x 10 in (254 mm), 4 x 4 in (101.6 mm), and 6 x 6 in (152 mm), you can cover all possible combinations with only five different lengths of the STR. Fewer screws are necessary to cover anything you may encounter on the jobsite.
Each pack of the STR includes a handy reference for the correct lumber combinations ideal for a specific length. Note that the required T-40 tip is included in each pack except in bulk.