mongos> db.activity_items.stats();
{
	"sharded" : true,
	"flags" : 0,
	"ns" : "500px.activity_items",
	"count" : 18364662,
	"numExtents" : 49,
	"size" : 1248797064,
	"storageSize" : 4878454784,
	"totalIndexSize" : 1199533664,
	"indexSizes" : {
		"_id_" : 646795184,
		"aid_1" : 552738480
	},
	"avgObjSize" : 68.00000261371541,
	"nindexes" : 2,
	"nchunks" : 32,
	"shards" : {
		"shard0000" : {
			"ns" : "500px.activity_items",
			"count" : 13923741,
			"size" : 946814400,
			"avgObjSize" : 68.00000086183735,
			"storageSize" : 4468617216,
			"numExtents" : 31,
			"nindexes" : 2,
			"lastExtentSize" : 750694400,
			"paddingFactor" : 1,
			"flags" : 0,
			"totalIndexSize" : 809219600,
			"indexSizes" : {
				"_id_" : 458869824,
				"aid_1" : 350349776
			},
			"ok" : 1
		},
		"shard0002" : {
			"ns" : "500px.activity_items",
			"count" : 4440921,
			"size" : 301982664,
			"avgObjSize" : 68.00000810642658,
			"storageSize" : 409837568,
			"numExtents" : 18,
			"nindexes" : 2,
			"lastExtentSize" : 74846208,
			"paddingFactor" : 1,
			"flags" : 1,
			"totalIndexSize" : 390314064,
			"indexSizes" : {
				"_id_" : 187925360,
				"aid_1" : 202388704
			},
			"ok" : 1
		}
	},
	"ok" : 1
}