The LineSPI has been a great tool for me, very durable and solid construction. I have used it for many years and it is a time saver for many applications. It is a dlc breakout box and allows scanner hookup. I use it when there is a "worn out" dlc on a vehicle, the linespi fits snuggly and allows me to continue diagnostics without worry of bumping the cable or repairing a dlc prior to diag. It also works great for the occasional vehicle with no voltage at the dlc to power up scantools. I can simply use the banana jacks and supply voltage without the need to first diagnose the circuit fault. If the circuit is shorted to ground, the linespi has an internal circuit breaker, so not a worry there. AESWAVE also provides this unit with custom switching to disconnect from vehicle power side of the dlc if the circuit is shorted. That is a real time saver for the technician! The most common use I get from this tool is a quick link to the vehicle networks, there are leds that will let me know if there is activity on the network, but it provides such a quick and easy access point for scope or dvom testing. I will add that I also use this tool when there is a procedure required for toggling dlc pin circuits to perform resets or enable relearns on certain vehicles. It is so much easier to drop in my leads and jumper those circuits "seven times in ten seconds" while sitting comfortably in the seat! I am sure there is more use for this tool than I have mentioned, but overall I give it an excellent rating!