Raymarine ST300, Thru-hull Shorty [E26008]ST300 Thru hull Shorty The S300 ST300 speed sensors are our lowest cost and shortest thru hull speed sensors. As part of our Shorty Series, they are designed for boats with low headroom. The plastic P371 low profile outer housing option is nearly flush and minimizes drag with only 5 mm (3 16") extending outside of the hull. The plastic P398 countersunk outer housing option mounts flush, eliminating turbulence for more accurate speed readings.