Please allow 1-2 weeks for shipment. Each 16 x 10.5 inch flat contains 6-15 matching pairs each measuring between 2.5 to 5 inches in diameter with the smaller diameter pairs used to fill holes in the flat. Most are quartz lined and measure between 2.5-4 inches in diameter per half but some do have calcite and/or pyrite as well or may be lined with calcite entirely. NO chalcedony geodes! We can honor requests for flats containing mostly all smaller or larger pairs or in a specific size range, but please allow a few extra days up to a week for shipment for us to make flats of requested size depending on what is on hand - please add a note in your Order Instructions when you check out with any special requests. Most orders not requesting specific sizes receive a mix of sizes mainly between 2.5-4" diameter.