The minimum annular ring on a plated thur-hole is the minimum amount of copper (at the narrowest point) between the hole and the edge of the pad after plating of the finished hole. MIL-STD-275E and IPC class 3 calls for a minimum annular ring of 0.05mm (0.002") edge of hole to edge of pad. MIL-STD-275E also call out 0.005 inches for via to trace distance.