These spring-loaded test Pogo / probe pins that are normally used for testing circuit boards or programming via electronic JTAG interfaces. They also make killer-looking feet!

This model has 6 grooves tapering to a point on a 1.5mm (0.59") diameter head. The outer shaft diameter is 1.01mm (0.040"), overall uncompressed length of 33mm (1.3") with 6.5mm (1/4") travel.