Subaru's driver controlled center differential works fine in most situations. However, if you have swapped your motor or transmission, or simply want more control; then the DCCDPro Spiider is what you need. From automatic to manual adjustment allowing you to operate at fully locked or unlocked levels, the Spiider gives you the control you seek.
DCCDPro has other products too, like the VSSPro (measures speed from the ABS allowing tire and wheel sizes to not impact speedometer readings or the ECU) and the FuelPro (ensuring a constant fuel stream into the engine without cavitation). If you have modified your ride or simply want consistency and control in your hands then DCCDPro is the answer. Canadian made since 2007, and available from your friends here at Four Star Motorsports.