Ease of Use
The Fenix BC21R clicks easily between its five modes with an on/off button that glows in the dark. The light mode switch is tactile, making it very glove-friendly for both regular-weight cycling gloves and heavier-weight cold weather gloves.

To turn it on, press the switch for a half-second until it powers up. Press once to activate the red sidelights only. Press again to switch through Low, Medium, High, Turbo and Flash modes. Enhancing simplicity is a “memory” mode that remembers the last mode used for the next time the light is turned back on. To turn off, press the switch for a second and then let go.

Beam Quality
The Fenix BC21R has an outstanding beam projection that is excellent for urban riding, general bike commuting and mountain biking on trails or rural roads. The key is in its Optimized Dual Distance Beam system. A series of grooves on the top one-third of the lens redirect a portion of the light downward on the path right in front of the bike while the lower two-thirds of the beam project light down the trail and with a relatively wide angle. 

Run times vary depending on the selected brightness mode but the flash mode, which rapidly alternates between 380 and 100 lumens, carries the longest-lasting use at nine days running sixty minutes each day. This is the longest burn time of all the lights in the test in this mode.

Features
The waterproof Fenix BC21R provides five brightness modes: Turbo (880 lumens), High (380 lumens), Medium (200 lumens), Low (100 lumens) and Flash (alternating 380 lumens and 100 lumens).

The flash feature of the Fenix BC21R rapidly alternates between the High and Low setting, which is effective in catching the attention of motorists. The flash feature is also the longest-lasting on a single charge. Our tester’s bike commute takes thirty minutes each way. Using the flash mode only, the Fenix BC21R went nine days before it needed to be recharged.

A cyclist will also get the longest-lasting light time with the Fenix BC21R thanks to the spare 18650 rechargeable Li-ion battery. Its small size means that the cyclist can easily carry it in a seat pouch or even a jacket or pants pocket.

To charge this spare battery, simply insert into the light and charge as normal. The Fenix BC21R also has a unique power-saving feature called Intelligent Output Downshift. When the battery level is lower than twenty percent, the light will “downshift” to a lower setting to extend ride time. This alerts the rider to recharge soon or replace with the spare battery.

Charging is simple and straightforward via a standard USB cable. Charging time from a completely dead battery to full strength required approximately four hours and thirty minutes when plugged directly into the wall.

An additional feature on the Fenix BC21R is in the Optimized Dual Distance Beam system. On the top one-third of the lens are a series of grooves that redirect a portion of the light downward on the path where the cyclist needs it, while the lower two-thirds of the beam project light down the trail and at a relatively wide angle.

For enhanced safety on urban streets or trails, the Fenix BC21R is equipped with red sidelights that provide 180 degrees of visibility. They are activated when the light is turned on and remain illuminated in all five light modes. When the light is in flash mode, the red lights flash too.

Of all the lights in the test that have 180-degree visibility side lighting, the Fenix BC21R’s is most impressive because it’s the largest and most noticeable.

Versatility
The Fenix BC21R attaches to the handlebars via a quick-release rubber ladder mounting strap. The rubber strap contains ladder-rung notches to ensure the light is secure however the materials are not as firm as that of the other lights in this test introducing concern for long-term durability, although it did work fine for the duration of the 4-month test period. To their credit, Fenix does include two straps in the box.

Once attached, our tester found that the light stayed firmly in place, even when riding over bumps or on a rough bike path.

Bike light theft is a reality and it’s always a good idea for a cyclist to remove a light if they will be away from the bike for any length of time. The Fenix BC21R makes this easier with a quick-release on the mount, which allows the cyclist to simply lift the plastic “trigger” and pull to remove just the light. The mount itself stays firmly on the handlebar.

Changing the light between bikes is very easy and requires no adjustment in the mount. A helmet mounting kit is not available but this light can be used for mountain biking and as a handheld flashlight.