I already have white eagle eye lights fitted the front of my bikes to give me extra see-ability (essentially daylight running lamps - always on when the side light/head light is on) , but after reading Ducks post:
https://www.k100-forum.com/t13050-my-latest-and-greatest-led-brake-and-tail-lighting-simple-and-dirt-cheap-to-boot#154306

I ordered 2 pairs of the eagle eye red lights to fit to my bikes for use as rear fog lights. Having order them in early Nov 17 (via Amazon from China) they eventually arrived on 17 Feb 18. Communication with the vendor was actually very good, but it took the third try to result in them actually getting to me (Perhaps the first 2 sets are still floating around the worlds oceans in a lost container?). The vendor actually put an extra 2 pairs of lights in the final package as way of compensation (nice gesture)

https://www.amazon.co.uk/dp/B00E0FR7QG/ref=pe_3187911_185740111_TE_item

Anyway, today, I fitted the first set to Heidi (Gretel will get hers tomorrow) and am very pleased with the results. 


I mounted my lights at the top of the rear fender/mudflap (drilled 10.2mm holes just below the registration plate) and, running a wire up along the left hand frame (black tie wraps of course) connected them via an ignition switched power supply to a switch (also from Amazon - China) mounted as high as possible on the right side of the handle bars. 
https://www.amazon.co.uk/dp/B01EYDPVKW/ref=pe_3187911_185740111_TE_item

(It's starting to get busy up front!)

I went for an ignition  switched power supply to protect my battery from fiddling fingers while the bike is parked up) - I also fitted an in-line fuse (just in case).

I didn't go for the flashing option as per Ducks post, but now have a manually switchable, high intensity, rear fog light which definitely will make by back end more visible during those seasonable fog patches. Total cost £4.74/bike (and two spare pairs of eagle eye lights as a bonus). Ideally, I would have a LED indication to warn me that the fog lights are on...but I like to think that I'm not a stoopid as the rest of the road users out there and am in control of what I'm doing.

Both bikes now done...so much quicker doing the second one. Another bitterly cold day with bright sunshine and blue sky and not a hint of fog in the forecast this week!!

A view from the back...


...and the view from the front (these led lights are always on with the head lights)


Fog off...


...Fog on!

(Doh - must rub out that pencil line!)

By the way - anybody heard from Duck lately? - last post was Oct 17 and there are no details of the date of his last forum visit. Hope you're OK mate and just hunkered down for the winter. It'll soon be spring!!

Great idea and well set up. We need all the protection and prevention measures we can think of to survive.

On the rare occasions we get fog around my place, you do notice vehicles with the rear red light.

Nicely done!

If you want to sell off the spares some Guinness/pudding/steaks can be arranged....!