The Turbo 4Lane Timer (complete with timer module, bridge modules, one-sided display of 4 lanes, start switch, ir emitters and hardware), Custom Carrying Case, Your choice of Software, and a serial port computer cable.
Separately these would cost you $406, so you save $37!
The difference between the DerbyPak 1 and the DerbyPak 2 is whether you are using a USB port or a Serial port.
Be sure to choose your lane spacing (3.25", 3.5", 3.75" or 4.0") and your choice of software.