Great collar, size is tricky
So first of all, I LOVE this collar, great idea, great quality, super useful.
On the downside is that after reading all the reviews and seeing that others had had problems with the collar being too big I decided to go for a medium. I have a lab puppy, she was 7months old at the time I bought the collar and it was a little snug on her. I kept it because we REALLY needed it right then.
She's 8.5 months old now and still fits snug, I am hopeful she won't have a HUGE neck, but I am afraid I'm going to have to buy the Large pretty soon here.
It is worth to say also, that we couldn't keep her out of the water...she jumped in and we called her out right away. When she came out the collar was wet and still working so it can take a little water.
We were able to see her from far so it was really good, it definitely gives you peace of mind being able to see your dog in the dark. We've used this collar for several camping trips and we only put it on her at night a total of probably 30hrs and still working fine.
I would definitely recommend, beware of the sizing though. When in doubt go for the larger size because you can make it smaller. Do not cut it if you have a puppy unless you are absolutely sure how big you pup's neck will be.