No special tools needed for installation. The switch replaces your existing stem cap and headset preloading bolt perfectly, and installs with a 5mm hex key and your existing star nut (star nut has to be hammered down to 45mm below top of steerer). An easily removable, polished cover hides the bolt when installed. Weighs only 55g including the bolt and cover.

Comes with a plug-in, two-wire harness premade with corrosion-resistant connectors and enough wiring to hook up to your generator hub and headlight. Since the harness plugs into the switch, the switch is super easy to repeatedly remove and reinstall, as would be necessary for Rinko bikes. When the switch is installed, it is impossible for the wiring harness to come loose. The wire itself conforms to military aircraft specification, and is thin and super resistant to abrasion. Check out our other installation hardware for integrated lighting here.

Made to fit 1" threadless steerers and stems. If you have a 1" steerer and are using a 1-1/8" stem with a shim, the shim must be even with the top of the stem or higher when preloaded.  If you have a 1-1/8" steerer, you will need to purchase the TMAT stem switch adapter for 1-1/8" steerers (see below).

Made in USA. 2 year warranty. $149 USD

The TMAT stem switch controls your bicycle's generator lighting system from a safe and convenient location. It allows you to activate your lights without reaching for the headlight's built-in switch (if it has one) and putting your fingers dangerously close to the spokes. It mounts ingeniously in the steerer tube of threadless headset-equipped bikes, and replaces the stock stem cap with a classically inspired and attractive rotary stem cap with knurled sides.


The TMAT stem switch was designed from the ground up like no other bicycle lighting switch. It is based on hermetically sealed, magnetic reed switch technology-- no exposed contacts, and has been rigorously tested, both on the bike and in the lab, to withstand the harshest, most punishing cycling environments. Brutal lab testing included a three-hour, 900-RPM orbital shake test, extreme high and low temperature tests, and an extended water submersion test. The switch is completely impervious to water-- it even works when submerged in water.


The rotary cap mechanism was carefully designed and tuned to have the feel of a high-end 70s stereo component knob, and was tested through 10,000 cycles before being incorporated in our early prototype to ensure long-term reliability. 

Installation instructions

TMAT stem switch adapter for 1-1/8" steerers

This adapter lets you install the TMAT stem switch in bikes with 1-1/8" steerers. The adapter is designed to fit the switch perfectly and add only 1.25mm of height to the switch, while retaining the ability of the switch to pre-load the headset and stem (see adapter, bottom right, and installed on a VO 1-1/8" stem, bottom left).

For more info and photos of the TMAT switch with adapter on a 1-1/8" steerer, see this blog post.

Made in USA. $19 USD