Various probe covers for the Welch Allyn tympanic thermometer range.Pro 4000 Probe Covers: are only compatible with the Pro 4000 Thermometer and the now obsolete Pro 3000 model, Pro 6000 Probe Covers: are compatible with both the Pro 6000 and the Pro 4000 Thermometers, Yuwell Infrared Ear Thermometer is compatible with the Pro 4000 probe covers.