I have been wearing Nippies (http://www.amazon.com/Nippies-Skin-Reusable-Silicone-ADHESIVE/dp/B001PU9A9Q) for several months and really like them, but decided to try these because they're less expensive and were recommended by a Nippies reviewer.  I really wanted to love them, but they just don't work well for me!

These Spicy Spot nipple covers are a lot thicker than Nippies, but much more transparent: if I wear a light-colored shirt with the Spicy Spot covers, you can see my nipples clear as day (compared with not at all when I wear Nippies).  Also, their thickness causes them not to adhere very well; I kept having to press them back on during the day, which must have appeared as though I was feeling myself up in public -- how embarrassing!  They also have this flower shape which is clearly visible under form-fitting shirts.

I wish I'd liked these more, but I will be staying a Nippies customer!  The Nippies brand has provided me with much better coverage and staying power, and it's worth the extra money to me.