There are three types of Train Buffer Beam with Sealed Magnets:
Type 1: 64424c01 (2005-2009) has a metal pin with a screw head, and the buffers are open on the underside
Type 2: 91968c01 (2010-2016) has a metal pin with a flat head, and the buffers are open on the underside
Type 3: 29085c01 (2016-) has a metal pin with a flat head, and the buffers are closed on the underside
The image on the right shows all versions. If unsure, use the modern version 29085c01.
Click on a colored part below to see the Sets and MOCs that use part 29085c01 Train Buffer Beam with Sealed Magnets [Type 3 with Closed Bottom] in that color. You can find an overview of all LEGO Colors here.
If a color is missing, it probably needs to be added to a Set Inventory.