Drop Thru Risers are sold in groups of four 4 which will be enough for two trucks. These risers are designed to work with the Loaded Dervish, but also work well with other Drop Thru style boards.
If you are using Randal or Paris Trucks, these risers require no modifications.
For Bear Grizzly Trucks, cut an additional slot the same size as the original just towards the middle of the original.
For other trucks a steady hand and a sharp knife will be required.