GETTING MY SOLAR PV HARNESS SUPPLIER TO WORK

The MC4 solar connector developed in 2004 can be an enhanced Variation in the MC3 connector, that includes a 4mm2 Get in touch with pin, an productive safety system, as well as a useful set up that turned it into a regular in the solar sector. This is a dumb question but I’m not solar panel savvy. What do the rubber plugs at the end of solar