Isometric Cylinder
To try a cylinder, select the Isometric Cylinder tool and click and drag as though you are creating an isometric ellipse in front view. Once the circle is created, release the mouse and immediately drag away from the circle without clicking to create the cylinder depth. The cursor will follow the isometric angle. When the desired depth is reached, click the mouse to finish the cylinder. You can hold down the command/control key to start with the side face or alt/option key to start with the top face of the cylinder (as shown). Remember to click to finish creating the cylinder depth before deleting or choosing another tool.

To numerically create the cylinder in scale, click once on the document. The cylinder face's center point will be placed at your click point.