Commands associated with one or more logical block addresses are received via a host interface of a storage device. A fluorite is proposed, in which the standard deviation of the surface areas of the Voronoi regions in a diagram from a Voronoi segmentation of the distribution of etch-pits in the plane is 6,000 \u03bcm2 or less, or, in which the standard deviation of the distances of the Delaunay edges in a diagram from a Delaunay segmentation of the distribution of etch-pits of the plane is 80 \u03bcm or less. A pair of left and right standing frames may be disposed on the outside of the seats, and the upper end parts of the pair of standing frames may be connected by a cross frame. The spring member bears against the blocking surface, and said pole extends through a washer, a spring member and the through hole of the base, the extended end of the pole engages with the second blocking member.