I needed to replace the previous safety light for my dog which was from a different company, and decided to try the Dog Nation version. The size of the light is well suited to my American Staffy, and it is really bright so he is easily visible when it is dark. My dog's collar is not from Dog Nation, so it doesn't clip on as it is supposed to. However, I put a cable tie around the collar and it is easy to attach the light onto it. I can't comment on water resistance yet as there hasn't been much rain. I use the non-flashing mode because the light is very bright, and is hard on my eyes when in flashing mode. The light requires 2 x C2032 button batteries which are readily available. Overall I am happy with the light but gave it 4 stars because it is designed to fit only Dog Nation collars. I don't need to spend extra money when I have a perfectly good collar already.
I have a black pug and at night time when I let him run in the park, sometimes its really hard to see him. this Safety LED Light is the best thing, I can always see where is he in the dark and its best for the cyclist to see him too when they are crossing the park.