A:AnswerThe adjustable strap can probably go up to 3inches in dia- wouldn’t go more-
Do not know if it’s waterproof, haven’t had it out in the rain-
I like the rear light, stays on, flashes!
Front light is powerful enough-
A:AnswerTHE FRONT LITE IS A CREE LED AND IS VERY BRIGHT. AS A FAR AS LUMENS OUTPUT BASED ON SIMILAR LIGHTS 300 TO 600 LUMENS IS A ESTIMATE ONLY. YOU WILL BE VERY IMPRESSED WITH THE LIGHTS POWER. FOR THE PRICE YOU WILL BE VERY PLEASED. IF YOU DO NOT LIKE IT YOU CAN SEND IT BACK FOR A REFUND. EXCELLENT LIGHT SET AND GREAT PRICE. AND IT IS SIMPLE TO INSTALL. BEST REGARDS.