3-way and 4-way Stopcocks, what is the difference?
Both have two inlet ports and one outlet port. Visually they look identical. A 3-way stopcock must have one of the three ports ‘off’ or closed. A 4-way stopcock allows one port to be ‘off’ or in a 4th position with all three ports open.
Braun 4-way stopcock with male luer lock fitting.