Why are the eighteen beads of Lingyin Temple big and small?

The growth environment, material selection and bead shape of each seed are different. The eighteen seeds of Lingyin Temple are all natural creatures, and the growth environment, nutrient composition, illumination and other factors of each seed are different, as well as the selection of materials and the types of beads. So there will be a slight difference between each string of eighteen seeds. So the eighteen beads of Lingyin Temple are big and small.