These are AMAZING!  I wear a UK 30GG (US 30J, and sister size US 32I, 34H, 36G, 38DDD) and got the DD size because it was the biggest size available when I ordered.  Writing this review I can see that a DDD size is available and I would definitely like to try that out too.
I've worn the DD size for 7 hours of running errands, going back and forth between air conditioning and 95F outside.  They have stayed pretty sticky despite sweat.  They are easy to apply.  When I first applied them, I had to re-adjust each side 2-3 times and they stayed sticky.  They stayed put throughout the day, but I have also been able to lift the top portion and readjust throughout the day.  These are completely invisible under silky clothes and provide ample coverage to prevent headlights.  It is made of a very thin (no padding, but full coverage), non-transparent silicone material.  They package said that there are non-adhesive centers for your nipples, by my set is completely adhesive.  I actually like that it is totally adhesive because it gives me more application options for different silhouettes.  I have used similar "lifting" tapes and products, but none have held up to the weight of my breasts (and I know many women have heavier breasts than me).  I think these are a great addition to my lingerie drawer in addition to a traditional sticky bra with a center clip-- these do not give you the cleavage effect of a normal sticky bra, but give great separation.