I had tried a patch from another website that had a tear-dropped shaped hole in the center of the patch to allow the probe to go through, but that shape allowed the Dexcom glue to touch my skin and still created a rash (albeit, 95% smaller than before) - but the pre-cut out center hole allowed a rash to that itched like crazy, and their patch began to fall off after just one day, requiring me to go out and buy "overlay" patches. THIS patch, however, did the trick! It has no center hole pre-cut out, as the probe goes through it, leaving no skin contact with the Dexcom glue. I'm on my final day of wearing this patch (10th day) and amazingly, no extra overlay patch has been needed, despite sweating like a storm in 90 degree heat to mow the grass and work on my car. No itchiness, either.
From a different site (BFD), I posted a 1-star review, and they refused to post it. I should have recognized something was wrong when their site only posted 4 and 5-star reviews.
If you're looking for a first-time patch to try, this is the one. It'll cover the Dexcom glue, and it'll stick to you. I have been dealing with mysterious welts from the Dexcom glue for months, and this patch restored my ability to use the Dexcom G6 sensor! And I'm impressed with this site's honesty in allowing low-star reviews, unlike the other site I purchased from.