The first small, 1" tall bump lets you know you are almost home; the second, larger, 2" tall bump lets you know of the correct "stop" position. The design of this Parking Mat prevents it from sliding around because the tire rolls onto the leading edge, holding it in place. Red and white stripes makes it easy to see, too. Heavy-duty double-sided mounting tape to secure the Parking Mat included. 11" x 21". Choose from black, red, or high-visibility yellow.