When selecting the best fully insulated female spade connector, it is essential to consider the wire size (mm or AWG) and the tab size which it will likely be connected. The width of the receptacle should match the width from the tab, as well as the thickness from the tabs can vary greatly. Common tab sizes include .110 (2.8mm), .187 (4.8mm), .205 (5.2mm), .250 (6.3mm), and .375 (9.5mm). Proper selection ensures a good and reliable electrical connection.