A pool thermometer I purchased, and INKBIRD wireless pool thermometer, had a really small attachment point for tethering to the sidewall of the pool, and if left free roaming, it would always go out of range of the wifi gateway, and eventually to the skimmer basket.  This was a quick fix to allow a ring with a larger tether point. 

After print, I just put a few dabs of hot glue in the collar, and put it on.  Could have been silicone caulk or similar, but hot glue was the quickest method.  

As it is an outdoor item, printed in ABS .6mm nozzle and in the orientation as given.  No supports or brim needed.