The rubber tubing will go threw the adjustable part so you can make it light up the whole collar. Someone said that the collar was only lighting up half, because of them having to size it. If you read the instructions it will show u this. & yes the collar is BIG. I have a 85lb lab and got a Lg & it fit him but I think I will order a Med this time. The collar has been great! My dog swims with it all the time and I have had it for about 6wks & it still works fine. The collar gets dirty and makes it hard to see the light but I just wash it and its good as new. The only reason Im getting another one is because so many of our friends want them so Im stocking up to hand out so they can all be seen and safe.