Check the listing for details. Apogee Instruments Oxygen Sensor / Meter Diffusion Head AO-001. Condition: New. Listed at 34.99 USD. Messages are responded to Monday-Friday 8 AM to 4 PM Central Time. Please message us for additional photos or details. If you would like expedited shipping, please message us BEFORE placing the order so we can add the shipping service/cost to the listing. We can ship on your FedEx or UPS account- message us BEFORE placing the order or leave a buyer’s note on the order with your account number. We do not use USPS. International orders are shipped using the eBay International Shipping Program. If you would like us to ship internationally with a different service, message us BEFORE placing the order. The diffusion head is designed for soil applications with an oxygen sensor. The head keeps soil and debris clear of the sensor opening to ensure accurate measurements.