I got these for Christmas and thought I would share my thoughts on them. I haven't tried nail art studs before but have used rhinestones. These might work well on denim nail polish too.
Both sets (black and silver) are in 4mm and are square studs, they are hollow and stick to the nail around the edges of the stud rather than the way a traditional flat back rhinestone would.
As much as I like the black studs, they don't obviously show up over black polish. Which is why I was also glad to receive some of the studs in silver, these of course show up really well on black polish.
Inside each pack are around 100 studs and depending on how you remove them they are reusable which is always a good thing!
Nails Inc / Kate Spade - New York Noir
BK - #20 (Neon Orange)
I wanted to do some nail art using these studs, as I didn't have any in orange to pop over the black polish I just painted a couple of the silver studs with an neon orange polish and that worked really well and was quite effective.