1. F One is so far one of the best file I’ve used. It can go smoothly in even narrow and curved canals. High cutting efficiency, very safe file. But I use it in for sure after getting patency with k 10. 2. AF Rotary & C-path files are also very safe, useful in very narrow calcified canals when the dentine is very hard. 3. Fanta hand files (K or C) are very safe too, I’ve never had file separation even in most difficult cases, while got many K file separation from other brands. The good thing about these files that they got untwisting before separation, so good safe indication to replace the file. File C is very efficient and I use them in every case due to their efficiency.