The Model 37 Classic Slide tube features a threaded nut on the rear and a bar Heliarc welded to the tube. This tube has been on most Model 37s throughout the years of manufacturing. ****Different years of manufacturing require different lengths of the tube. To ensure proper fit, please refer to the length descriptions before proceeding. Depending on condition, discontinued parts may possibly be repaired by Ithaca, but require the actual wood forend, original tube, and nut to be sent to Ithaca Service for proper fitting.