You are looking at a mint in the package K-Line "protector" lock on. This lock-on works with all O gauge tubular rail no matter the manufacturer. The neat thing about this lock on is that it protects your track and power pack from voltage spikes, power surges, etc. Think of it as INSURANCE for your trains and equipment.
Guard your valuable on-board electronics with the Protector Lockon(TM). The illuminated Protector works with any O Gauge track to absorb power surges and guard against power spikes. Includes easy-to-connect banana plugs.
If you have K-Line Shadowrail and need more, now is the time to buy it since K-Line is no more. Lionel, who now "owns" K-Line, will probably not continue its track lines.
Note: I do not think this would be easy to hook up to Lionel's new Fast Track--it works with everything else that I am aware of.
THE ITEM YOU ARE CONSIDERING IS THE CONNECTOR IN THE PICTURE--THE ITEM THAT CLIPS TO THE TRACK. THE LOT DOES NOT INCLUDE THE STRAIGHT TRACK SECTION PICTURED in the stock photo.