You need to recheck the Marstar site. The part you need is illustrated as GAR037 Handguard ferrule, rear, but the illustration shows a lower band. They show this part as being in stock. This is different from the front handguard ferrule.
I double check and I called. True the picture on part GAR-037 is a lower band but it's the wrong picture for the part on the schematic. I would need part GAR-036 wich is not in stock. Anyway I needed some accessories so I ordered from Brownells and Numrich. Shipping is expensive but hey gotta complet that rifle and their lower bands are brand new so are all my metal parts on my stock. Thank you for the input tho