A fantastic price on a fun product!
I got two pairs, which is good for me since I've got my nipples done. They're probably 15mm. They do glow well. You have to keep in mind that they need to absorb direct light in order to work!  Some colors don't glow quite as well as others. This is to be expected in all glow in the dark products. I would definitely recommend this!
Rating: 5 stars