Factory LS cylinder heads are machined with metric M12-1.5 coolant sensor ports, so your factory Small Block Chevy sensor won't thread in to them. This adapter allows you to keep your original sensors and integrate them into your swapped LS engine. | Adapter has a female 3/8" NPT port, 1.7" deep. Refer to thread chart to check your correct fitting size. (Use PN# 551179 for .85" deep adapter for shorter sensors) | Made in Wichita, KS from aerospace grade, USA billet aluminum | This adapter will fit all LS series engines. | Adapters are sold individually, and include 1 sealing washer