I have a set of 1/4" grommets. The curtains I use have 4 layers of fabric at the top. The 2 layers of the face material are the thickness of regular fabric, while the other 2 are thick fabric with sun protection. The fitment bushings was very difficult. I'm afraid they will fall out. I think a bigger bushing would be better. The problem installing these bushings was due to my inexperience, but the installation instructions were basically incomprehensible.!