Quad scull

A quadruple sculling boat, often simply called a quad and abbreviated as a 4x, is a racing shell used in the sport of competitive rowing.

Racing boats (often called "shells") are long, narrow, and broadly semi-circular in cross-section in order to reduce drag.

Quad sculls is one of the classes recognized by the International Rowing Federation and the Olympics.

[1] FISA rules specify minimum weights for each class of boat so that no individual will gain a great advantage from the use of expensive materials or technology.

In sweep oared racing the rigging means the forces are staggered alternately along the boat.