Airtag Dog Collar Holder Case 2 Pack for Apple Air Tag, IP68 Waterproof & Aviation PC Material 360° Protect Your Cat Dog GPS Tracker......

This is great for a very large dog collar. The holder itself screws down onto a gasket which will keep it water tight. They include a spare gasket which is a plus. Material is hard plastic which has no give to it. I took off one star for this reason. hese need a little flexibility in my opinion. The round textured shape of the lid make it easy to screw down for the best possible seal.

These AirTag holders each come with 2 washers. I think they are neoprene but whatever the material one is seated properly inside the base. That one is no problem. The other, however, is for what I will call the "cap" which is the screw on top you attach after you insert the AirTag. You cannot screw on the cap until you get the washer seated properly on the cap. It's so frustrating that I was tempted to go with a 1 star rating at first because I could not get the caps to close at all, rendering these holders useless. However, after working the washers flat I was able to finally get the caps to go on tightly. With an AirTag holder this process should only need to be accomplished once, or at least until the AirTag battery gives out which is usually more than a year. So even if it is annoying and time consuming if the end result is a waterproof AirTag holder for your dog's collar that's fine. However, no matter how carefully I got the washer in place and how tightly I screwed on the cap the end result was still an AirTag holder that would not fully prevent water leakage. I didn't drop this down to 1 star because if your dog isn't a daily swimmer but only goes out in the rain this will probably work well enough. However, if you have dog that jumps in the water at every opportunity this is probably not the right AirTag holder for your dog. If you go with it anyway, open it up after the first such swim and make sure there is no water in there. I can tell you from experience, if water gets inside a "waterproof" AirTag holder and sits there undiscovered for days it will eventually kill your AirTag. AirTags are reasonably water resistant on their own but they don't do well directly exposed to water for days at a time.