Generally speaking, it is advisable to buy individual Forstner bits rather than a set. The bits in a set are usually of lower quality that won't hold an edge well. There are exceptions such as Freud, Fisch, and Colt, however a set of high quality Forstner bits is likely to be expensive. My favorite are Colt bits ... they stay sharp for a long time if they aren't abused and they are easy to sharpen with a diamond card.