Some of my drill bit sets have broken bits or are too small and I needed hardened steel so I bought this set. I had to increase the center hole of my RC wheel to 7/8 inch to fit my car. I also had to drill some holes in my RC bike for the fenders and exocage. My only complaint was having to progressively drill through my RC body. , as the large parts tend to run around. I don't think it's those bits, it's probably the slick plastic case. I know all my holes were on the plastic but they seem very sharp. I definitely recommend this product.