MC3 to MC4 Solar PV Adapter Female MC3 to MC4 Female Adapters are used when trying to join connectors from the module that do not match up with the inverter. All 88.3344-F adapters are made with PV-Wire that has an extra layer of insulation for use on ungrounded arrays in conjunction with transformerless inverters. This type of wire is required to meet the 2008 NEC if you are using a transformerless inverter. Male or Female? At first glance, the distinction between male and female connectors is somewhat counter-intuitive. "Male" or "female" refers to the metal pins inside rather than the actual housing of the connectors. The housing of the male connector has a large opening at the end with the actual pin inside. The connector of the female, however, has a long tip goes fits into male connector when the two are mated. If you have any questions before you make a purchase, give us a call so we can help you understand the difference between the two!