This is the feed ramp used only on the plastic lower model semi-auto carbines using the Thompson SMG magazine, no feed ramp is used or required on the metal lower models that use the M3 Grease Gun magazine. These are not the original black plastic that wears so quickly, these are made from a modern heavy molecular weight polymer that is very slick and ideal for a feed ramp. This material was just not available at the time or they would have used it. There is also a metal plate that should be present on your lower, it is below the feed ramp. If you need this also let us know we usually also have these in stock.
