Diamonds have their sparkly shine due to facets. These are the surfaces on the stone that is plain and reflect more light. The more facets a diamond has, the shinier it is.u003cbr/u003e3D means that the resin drills have 3 facets on three sides, making it a total of 9 facets. 5D refers to having 5 facets on each side, which is 15 facets on the drill. The latter one with more number facets is shinier.