I got the 4mm and 3mm crystals for my lobes, and the 2mm for my nose.
Putting them on was very simple, had no issues at all...
The flat back is comfortable, and the piece is very secure - doesn't open or gets undone by itself.
The pieces are very pretty but at the same time not "too much", and go well with any other silver jewelery I wear...
Absolutely love them!