Amos
That unit is wired to work with bikes with a separate regulator and rectifier.
When my K2 left the factory, it had both units - the original rectifier was fitted with the plastic connector; the regulator connected to the loom by means of three wires with female spade connectors on the ends (white, black and green). The unit on eBay takes place of both those bits, leaving just a green (earth) wire from the loom.
I've replaced my two with a unit that's very similar to the one in the advert, but I got mine from Silver's - and yes, it was about twice the price of the one on eBay. I dunno what the wiring arrangement on the K5's is like, but the modern solid state replacement is far more reliable (for me) than the original - it also doesn't require any adjustment (the original regulator can be adjusted).
The one drawback is that it's not a simple bolt-on job because of the battery tray design. Again, I dunno what the K5 is like, but the K2 has a captive bolt that holds a sub-assembly on to the side. I took the sub-assembly off, drilled the captive bolt out, drilled a second hole and put my own bolts through the tray from the inside.
I dunno whether you can see what I mean from this:
. . . or this . . .
(ignore the relays - they're installed to take the weight off the headlight switches, but I need to fit them properly)