Busch + Muller B&M Secula Plus

Busch + Muller B&M Secula Plus for post or stay, wire included

One of the very few dynamo taillights that'll mount to either a seatstay or seatpost. The mount swivels so that you set the light vertical. Like all B&M dynamo lights, it has a capacitor (standing light) that keeps the light on for 4 minutes after you stop (that's what the "Plus" denotes). Also features over-voltage protection.