THESE CASTERS ARE MADE FROM 6061 T6 ALUMINUM BAR STOCK.
THE STRUTS ARE SPRING STEEL.
THE BALL BEARING  CAN BE ADJUSTED FOR THE TURNING RATE THAT IS REQUIRED.  SPRINGS AND MOUNTING SCREWS ARE INCLUDED.
ALSO COMES WITH A SCALE LIKE RUDDER HORN.
WEIGHT - 5.75 OUNCES.