Why is the needle numbers in my owner's manuall have a two letter suffex? R1369MS, R1370MS, and R1368MS for example. Everything I read tells me there is only one letter after the four numerical descriptors except for the Honda manual & they give no explanation on what or why there is an (MS) at the end of the needle number. Ultimately, I am trying to figure out what number Sudco needles match up to these needles. Any help would be appreciated.