I recommend the Serfas UTL-6 Thunderbolt tail light. It's the same width as my aero seatpost and the rubber straps easily fit around. It's super bright and lasts a long time on the lowest blinking setting. 4-5hrs. Mine is 5 years old and going strong. Looks like the new version lasts even longer.

https://www.serfas.com/...l-6-thunderbolt-usb/

- Justin

I actually have a seat post light and two Serfas Thunderbolt 2.0s on my seat stays. The 2.0s are brighten and last longer . . . I love them!!

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David
* Ironman for Life! (Blog) * IM Everyday Hero Video * Daggett Shuler Law *
Disclaimer: I have personal and professional relationships with many athletes, vendors, and organizations in the triathlon world.

this one works great on my Trek SC
pretty cheap too
https://www.amazon.com/gp/product/B015IEJ0GC/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

The Lezyne rear light that was written up in the front page article here works pretty well on an aero section seatpost, just need to daisy chain a couple of the ubiquitous rubber loops together to make it happen...

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

If you don't need the Varia (which is AMAZING!!!), maybe you can just order the mount from Garmin? Fits my 2018 P3 very well.

I have a cervelo P3 and used a Knog Blinder https://www.sportinglife.ca/...jEAQYFCABEgItwvD_BwE[/url]

It was a good fit and came with two sizes of elastics for larger or smaller seatposts. Unfortunately I lost it by leaving it on the back of my truck and driving away (took it off when the bike was on the rack). I replaced it with two other Knog lights both of which said they fit aero seat posts but neither were big enough.

I daisy chained this one but it often falls out of its magnetic holder and I have to turn around and pick it up...so I wouldn’t recommend it. https://www.sportinglife.ca/...VEAQYCiABEgKLkPD_BwE[/url]

And the Cobber mentioned above was also not a large enough clasp/elastic. I put it on my rear water bottle holder and it fell off during a ride and I did t realize it till I got home so it’s gone now too.

The positive with these was no extra cord to recharge, the whole unit just plugs into a USB. f you can find the Mob light I mentioned above that’s the one I would recommend.

Jesus Christ...guy spends $10,000 on a bike and then does this. Lmao...

The Cygolite Hotrod is a simple, inexpensive option with several modes:
https://www.amazon.com/...icycle/dp/B013FIWQ5U

In my experience the battery doesn't last as long as advertised, but still lasts plenty for long rides (5-6+ hrs in steady modes, 10-15+ hrs in some of the blinky modes). Fits well on the seat post of my Plasma 5.

Topeak taillux 30. Its tiny, brighter than I thought, usb chargeable, and comes with several mounts including aero post. Its also super light and inexpensive

I have one of those

Like many USB/LED lights, you do NOT want to look directly at it when you turn on to see "Is this charged?" unless you want to see a bright green line in your vision for the next 5 minutes or so, while your retina reboots

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"What's your claim?" - Ben Gravy
"Your best work is the work you're excited about" - Rick Rubin

Have you seen this? The “wings” that latch on the aero post are adjustable.

https://www.guee-intl.com/products/aero-x/

I've got a lyzene light like that and have issues with the light twisting to the side. The rubber bit that hugs the seat post needs more depth to it.

Let me know if you have time to measure your clamp.

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Advanced Aero TopTube Storage for Road, Gravel, & Tri...ZeroSlip & Direct-mount, made in the USA.
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Beer and sleep won out last night LOL

I will get it to you tonight or this weekend

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http://www.TriScottsdale.org

Cateye Rapid X2 or Cateye Rapid X3
https://www.cateyeamerica.com/...2-Rear-LM-TL-LD710-R
https://www.cateyeamerica.com/...3-Rear-LM-TL-LD720-R

with Aero Mount CATEYE SHARP AERO RUBBER BASE FOR RAPID X3 / X2
https://www.cateyeamerica.com/...base-for-Rapid-X3-X2

Good light. Aesthetics are pretty low-profile, stealthy.

BTW, the Cobber is a good light for a ROUND TUBE ROAD BIKE. I've had many of them, but only for that purpose.

didnt read any of this thread, so i dunno if they have been suggested but i LOVE my see.sense lights. the newest generation comes with an aero seat post mount in the box... previous gen you had to purchase it separate but was worth it.

these lights are BRIGHT and have great patterns to get drivers attention.

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80/20 Endurance Ambassador

I've been using this on aero and round posts, and have had good luck with it for over a year. Rechargeable, bright and multiple blinky modes, lasts for 5+hrs, and should fit most aero posts well. I'm sure you could get a longer elastic band if needed. Can't beat it for $15! :

https://www.amazon.com/...geable/dp/B075474TBS

I'm also using the TraceR, its a great light. You can buy the saddle rail mount or use the gopro clip mount with a gopro saddle mount so the light is tucked neatly under the saddle, super clean.

I also run the Trace (front light) with the aerobar gopro adapter which is really tidy (when training).

I was skeptical, bought one, and I'm sold. I've been using mine for a couple of months now. Well worth the money.

Especially when riding my TT bike. It's really changed the way I ride, being aware of approaching traffic and not having to look back so much. And not just the radar aspect but the flash itself seems such that drivers tend to give me more room.

Edit: and to add, it works well on both round and aero seatpost. Easy to change between bikes with the 2 different rubber adapters (included)

My SC post measured about 60mm. I can try it on my friends p5 if that’s the same seat post.

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http://www.TriScottsdale.org

Can I ask the dumb question but how do you daisy chain bands to be long enough?

Put one circle thru the other than back thru the original, if that makes sense.

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http://www.TriScottsdale.org

Nah, it's a good question. Use a simple girth hitch.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

Interesting. What kind of seatpost are you putting it on? I tried it on 4 different types and didn't experience that...

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

That was a KEY pro-tip!

I just tried it with the various O-loops that came with the Varia, and it works great on a Cervelo p2 seatpost - thanks!

I was wondering why several folks on this forum said the Varia came with O-loops that worked fine with an aero post, but I could never get it to work. Girth hitch FTW!

Appreciated!