Dear Angela,

I have used these cups for all 4 of my children and have found that the leaks occur in the way the cap is twisted. The silicon nipple bunches slightly between the cap and the bottle. It is common to tighten more to prevent leaks, but in this case, don't wrench the cap and keep the indents on the nipple centered on the detents on the cap. I hope this helps.

Does any one have a site to purchase the nipple only? My nipples shred with use and need to be replaced often?

Alicia