Wago 215 banana plug
Banana plug with the patented cage clamp connection instead of screw connection. They are sold in various colours. Max. 2.5 mm² wire area AWG 13
This is a really practical accessory in the lab when you have wires (massive, stranded or flexible). The cage clamp (spring) can handle all sorts of wires, but only a single wire, not two or more. The 100% secure connection is achieved only with one wire. The square hole is for measuring voltage with a multimeter.