Lobster,

Piston Wrist Pins are either "fixed" to the rods via a press fit, and then pivot only in the piston, or the rods are bushed and the pin then free to float in both the rod end and the piston.

Some say that a pressed pin offers increased longevity, which may be better for a street engine. A floating pin offers less friction but adds expense and must be retained at each end, side to side, by clips that are installed in the piston.

In my opinion a floating pin offers little increased efficiency for a lower RPM street application, and a pressed pin rod offers increased stability.