Busch + Muller B&M TOPLIGHT LED LINE Senso - Battery Bicycle Tail Light

This model replaced a damaged  4D Toplight Senso  and it's immediately obvious how much more secure the design is—there’s an optional Torx T20 bolt used to secure the battery compartment to an internal metal nut rather than the 4D's wood screw through plastic, it's rated the same for battery life with one AA battery instead of two and is just as bright, and the mode select button is more reliable while the 4D's switch got permanently stuck in the first few months. Bit strange that the optional Torx bolt requires that you first drill a hole through the battery compartment cover, but not really a problem. The 4D required drilling two holes in order to mount it to the rack while this drilling is apparently optional, so that's actually an improvement. I'd recommend using the optional Torx bolt so you're sure the battery cover isn't going anywhere.Note: The slightly larger-diameter, rechargeable  Imedion 2400mAh AA batteries  fit with no problem. Purchased in 2011, they've all been cycled dozens of times and currently average 2240mAh—or >98% of their original average 2280mAh charge—with a  PowerEx MH-C9000  charger. I mention this because they're still the highest capacity LSD (low self-discharge) batteries I'm aware of and keep this light going longer than its rated 40 hours.

Lovely, surprisingly bright permanent light. This fit perfectly on to my Tubus Cosmo rear rack. The switch is a bit finicky, but this rear light offers surprising visibility. It does not flash, it is a solid light.

Love it. Does not blink, so if you want a light that blinks, get a different light. This is a german light, so is constant on and does not blink. It is quite bright and I like it.

Solid safety--great design-- pretty cool feature with the Senso mode. Light shuts down automatically if movement stops for a few minutes, and if it is light enough for a long period of time.

Already have one, so no surprise

I have tried a BUNCH of different blinkies. Seems here in the USA, the marketing hype is all about lumens one-upmanship. Make taillights so bright, motorists can see you a mile away. I can't deny, they get you seen by motorists, and they hate cyclists for it. It's ridiculous overkill. On top of that, you have to recharge them frequently if you ride every day.Germany has strict conditions and limits for bike lights (light pattern, brightness, etc.). The Topline Line Senso meets all of those requirements and is very visible in night/twilight conditions. I don't think it'll make you jump out much if you turn it on during sunny daytime conditions. The light "bar" projected from two tiny LEDs is impressive without being obnoxious.The best feature is the automatic sensor mode that turns the light on only when the bike moves and it's dark enough. Truly set and forget. A single AA battery lasts a long time. I ride 40+ hours per month and I'm still on the first battery. I do wish the light stayed on a bit longer on my AM commute before turning off when it sees the sun. If I can figure out where the light sensor is located/looking, I may put a couple Sharpie dots on the lens to make the sensor think it's darker outside and stay on longer.Oh, and this taillight fits perfectly on Racktime and Tubus rear racks or any rack with 50mm mounting hole spacing.EDIT: Drooping one star. Love this taillight at US $39. Went back to buy another and the price is now US $66. Cannot recommend at this higher price. There are better lights in this price range. Not sure why the price jump since Euro is falling against the USD.