I have a Blackburn mars 4.0 taillight hat has served me well for awhile. I am attempting to mount it on a bike that has bags and things in the way and it really needs to go on the rear rack bracket.

I could have sworn it originally came with a rack mounting option, I can't seem to find whatever adapter is required. After a long search online and in my parts bin I can find no trace of such a thing.

I would just stop searching but Blackburn says it comes with one, so do several reviews and product descriptions. Ready to just buy a new taillight....should probably call Blackburn and inquire first.

Any chance someone can confirm the existence of such a rack mounting bracket for the mars 4.0? If so where might I find one?

Also do you have pictures of the impossible to find small piece of plastic so I know what it even looks like? Many thanks.

Yes, they do have the mount. You can see what it looks like in the "manual" they have online.
https://www.blackburndesign.com/black...s/mars_4.0.pdf

The first Mars 4.0 that I bought didn't have a rack mounting adapter. When that one dropped off mid-ride one morning I had to pick up a new one, which did have the adapter. So, it might depend on when you bought yours. I got my "new" one about a year ago, if I recall.

I got mine shortly after they first came out, and it has the bracket. I have it mounted on my rack, though I had to modify it to get it on there rightside-up.

Thanks for the info, especially the .pdf. I called blackburn and they sent me the wrong part, called back and they are attempting to find the right part for me. They claimed that a part number doesn't even exist for that little square piece of plastic.

Told me I'll get a whole new light if they can't find that part...we'll see what happens.

Mine didn't come with a rear rack bracket, but my LBS modified my post-clip to turn it into one for a few dollars when I went in to ask about it. If you'd rather not wait to get the official part you could try that yourself, or see if someone at your LBS can do it.

Update: Blackburn came through, got the little part in the mail today!