Instructions
Look on the box for your "Rock Band" drum kit, or check the user's manual that came with it. These are the easiest sources for finding out exactly which model of drum kit controller you're using to play "Rock Band."
Examine the controller's drum pads. The original "Rock Band" model had 4 plain, gray drum pads that have a circle of color around them. "Rock Band 2" drum kits have a black dot in the center of the pad to show where you need to strike. Special kits like the Ion Audio Drum Rocket have more than 4 areas to strike, and the arrangement is double-decker with cymbals.
Check the stickers and fine print on the kit itself. If you can't identify the kit just by looking at it, there should be an identification label on it that states the model and type.