Sleek, compact and lightweight fetal monitors for antepartum of fetal heart and uterine activity made with the quality you expect from Corometrics. Wide beam 9-crystal Nautilus watertight ultrasound transducers provide the fetal heart rate and acquire the signal easily and quickly. Watertight Nautilus tocotransducers are flat for comfort and easy to clean.Corometrics 170 monitors come in two options: Model 171 single ultrasound for reliable non-stress testing, and Model 172 for dual ultrasound external monitoring for non-stress testing.