The Serfas TSL-1000 is a cool light. It dares to innovate where many others stay the same and just employ the latest LEDs in their old light chassis. It's a completely new light for Serfas with a tiny head unit much like the Lupine Piko and Gemini Duo, but this one is a little bigger and has air ducts to help dissipate heat.

What it really brings to the table is it integrates the awesome 50 Lumen Thunderbolt tail light in to the battery. This means that the commuter will have an integrated system with one power source. The tail light is one of the best in the business and can be visible from well over a mile away on a clear day.

Ok, more good news is that it delivers 1130 Lumens even though they only claim 1000. Such humility is to be praised in the light industry as it calls out those who wildly exaggerate their lumen ratings.

The beam pattern is awesome as you can see below. There is width and throw with two LEDs complementing each other to create a far and wide beam.

Run time is two hours and charge time is four hours on high. With the tail light flashing, the run time will hardly be affected. We suspect it will drop down by a couple minutes if the tail light is on solid.

It is a nice gimmick to integrate a tail light, but does it work? We think so, especially as a handlebar mounted light. The battery can be mounted on the seatpost and provide excellent visibility from the rear. For the helmet, we haven't tried it but the 80 gram head and the 140 gram body is not too bad for the helmet. If the battery is mounted on the CamelBak or jersey pocket, it will lose its visibility. Do cyclists want this kind of headlight and tail light integration and will they pay for it? We'll find out.


  • Price: $320
  • Claimed Lumens: 1000 Lumens
  • Measured Lumens: 1130 Lumens
  • Measured MTBR Lux: 110 Lux
  • Lumens per $: 3.53 Lumens
  • Lumens per gram: 5.14 Lumens
  • Time on High: 2 Hours
  • Charge Time: 4 Hours
  • Mounted Weight: 220 grams
  • Category: High End


  • Good innovation
  • Great front beam pattern
  • One of the best integrated tail lights
  • 220 gram overall weight is light
  • Excellent bar and helmet mount included


  • Helmet mounting the battery for visibility can make the system heavy on the head
  • Pricey at $320
  • We are uncertain if there is a demand for this kind of integrated product


An excellent bar mount is included and an independent helmet mount is available as well. The light can be aimed left to right.

Mtbr Light Meter Measurements

This light measured 110 Lux on our ambient light measurement facility. The light output measurement is performed by placing a Lux light meter beside the light. Both are pointed at the ceiling (five feet above) of a dark room. This measurement uses the ambient light produced by the bike light.

Integrating Sphere Measured Lumens

This light measured 1130 Lumens in an integrating sphere. Claimed Lumens by the manufacturer is 1000 Lumens. The Lumen-hour graph below shows how the light performs over the first three minutes of its battery cycle.

Compare all Lumen Tests here »

Tunnel Beam Pattern Photo

The location is useful since it has walls and a ceiling that can display a bike light beam pattern. The walls have a lot of graffiti on them and actually show detail when they are lit up by a light with a wide angle. Cones and targets are set up with the far target set up at 120 feet.

Compare all Tunnel Beam Patterns here »

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2014 Mtbr Lumen Tests »
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