The Colorado hookless cactus is a barrel shaped cactus that ranges from 1.2 to 4.8 inches (3 to 12 centimeters) tall, with exceptional plants growing up to 12 inches (30 centimeters) tall. Stems range from 1.6 to 3.6 inches (4 to 9 centimeters) in diameter. The stems have eight to 15, typically 12 or 13, ribs that extend from the ground to the tip of the plant. Along the ribs are areoles, which are small, cushion-like areas, with hooked spines radiating out, as described by Heil and Porter in 2004. There are two types of spines - radial and central - defined by the size and position on the plant (74 FR 47112). The two to 12 radial spines are located around the margin of the areole, and extend in a plane that is parallel to the body of the plant. The radial spines are white or gray to light brown. They are up to 0.67 inches (17 millimeters) long, and less than 0.04 inches (1 millimeter) in diameter. The one to five central spines, usually three, are 0.5 to 2.0 inches (12 to 50 millimeters) long, are generally longer than radial spines and extend from the center of the areole. The central spines include abaxial and lateral forms. Abaxial spines are typically single, point toward the top of the plant and are noticeably bent at the tip at an angle usually less than 90 degrees. Lateral spines are usually present in pairs on either side of the abaxial spine, but are more or less straight and diverge from the abaxial spine at an acute angle, usually 20 to 50 degrees. The flowers are usually funnel-shaped, but sometimes bell-shaped. They usually have pink to violet tepals, that are petal-like flower parts which are not differentiated into petals and sepals, with yellow stamens, the male reproductive organ of the flower, and are 1.2 to 2.4 inches (3 to 6 centimeters) long and 1.2 to 2 inches (3 to 5 centimeters) in diameter. The fruit is short, barrel-shaped 0.31 to 0.47 inches (8 to 12 millimeters) wide and 0.35 to 1.2 inches (9 to 30 millimeters) long.