Easy to insert and position, and has a large contact surface for multiple sensation capabilities. Smooth and solid.
It's 100mm (4 inches) in length, 20mm (3/4 inch) at its widest point and 14mm (1/2 inch +) wide where it tapers. For perspective, one picture is next to a standard #2 size pen.
Also comes with a removable long plastic handle for easy positioning.