Borgeson 3/4 DD X 3/4 Smooth is a steering universal joint used in custom or performance automotive applications. It is a single needle-bearing universal joint that connects a 3/4″ double-D shaft to a 3/4″ smooth (or round) shaft. The “DD” refers to the Double D profile of the shaft end, which has two flats on a round shaft. 

According to the official Borgeson website, the key specifications for the 3/4 DD X 3/4 Smooth steering U-joint include: