Very, very bright
Small
Light
Inexpensive (for the amount of lumens)
easy to attach and detach to bike. No tools necessary.
Weatherproof
Excellent light for commuting.

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Very bright light that lights up the night! Barreling down a long, steep, winding drop at 42 MPH at 5:30 AM it is good to be able to see road hazards with enough time to dodge them. After dawn, switching the light to flashing mode gets cars' attention and helps to keep me from being run over. For commuters having a bright light is more important in the day than at night. At night even a relatively weak light is visible but will disappear in the light of day.

The Ray IV is a big light in a small, light package. Attaching and detaching the light is very quick and simple and does not require the use of any tools. Excellent light at an amazing price!

Very Bright
4 Led
1500 Lumens
Great Acknowledgment from traffic
Keeps you safer on road

Not many, battery life a little shorter than Ray I and Ray II may be the only weakness.

Training over 80,000 miles over the past 3+years including trips from Florida to Alaska and Back, Florida to California and back, Men's Solo Race Across America, and Florida to Ohio and Back, I slowly began to take my safety more seriously. After getting hit by an S.U.V. on my second trip on the Florida to Pittsburgh leg of the Florida to California and back trip, never again will I not train with bright BikeRay Lights. Lights are not meant for the daytime right? Wrong! I got hit at 7 pm, a full 1.5 hours before the sun even set. It was a moderately traveled road called S.R. 121 in South Carolina near Newberry. The accident slowed me down and nearly put a end to my journey to California and back. I forged on and continued my 7,737 mile and 61 day cross-country bicycle camping trip and ended back home in Florida.

When roads appear nice or not nice depending on traffic, just remember that distracted and careless drivers can come at random. A road that may appear nice and relaxed can turn deadly in a matter of minutes due to a distracted and careless driver. A a cyclist, I must remember that while training, I am the smallest form of traffic on the road and need to be well seen. Riding with BikeRay lights, especially the brightest of the all (The Ray IV) will only improve my visibility and decrease my chances of getting hit and struck by an automobile.

I ride with BikeRay lights because I care and give a damn about my safety above all else. A BikeRay IV light and battery pouch will only be an extra pound on your bike will be the most beneficial pound you ever put on your bike, I guarantee it. When ever I feel vulnerable on the road to traffic, I keep the RAY IV on flashing. Some drivers may find it annoying, but as a cyclist I say the most annoying thing to vehicular man-kind is big steel-box automobiles: clogging roads, polluting the air, contributing to the nations obesity problem, contributing to the nations gas-financial crisis, and killing people.

O and just imagine, the BikeRay IV light not only keeps me safe and bright during the daytime, but at night the light is magnified to a super-bright beam that will definitely keep let you see everything in front of you and well seen by cars!