i use these "Original Instant Nail" for years
i bought them when it was only material they were selling, i never tried the pre formed or thicker thumb stuff
http://guitarplayernails.com/store/
for me the fiberglass wrap didnt work, instead when the physical nail breaks on the side i glue on top a piece of an artificial nail and i file the edges down so it doesnt catch the string when i use the top of the nail.