Each cylinder is hand crafted and made of the finest, industrial strength crystal clear acrylics. The cylinders are tapered toward the top to match the natural anatomy of your penis and are flared at the base for maximum comfort.Each cylinder contains a state-of-the-art air valve which allows for quick and easy disconnection from the pump while maintaining pressure within the cylinder. Whether you choose the electric pump or the basic or deluxe hand held pumps you can be assured that you have been fitted with the best cylinder on the market today.Sizing:Penis pumping cylinders are sized in relation to the girth (girth is the circumference, or distance around, the penis) of an erect penis.To determine which cylinder size is right for you, measure your girth at the thickest point of your erect penis. The thickest point of the penis varies among men, and may or may not be at the head, middle, or base of your penis.To measure your girth, wrap a string around your erect penis, and use a felt-tip pen to heavily mark the point on the string where it crosses itself. Then straighten the string, and use a ruler to measure the distance between the two marks. This measurement will represent your penile girth.Whether your measurement is in inches or centimeters, use the sizing chart or the cylinder size calculator below to determine which of our cylinder sizes is best for you.Cylinder Size Fits Girth Up to1-1/2" 4-1/2" (11. cm)1-3/4" 5-1/4" (13.3 cm)2" 6" (15.2 cm)2-1/4" 6-3/4" (17.1 cm)2-1/2" 7-5/8" (19.3 cm)2-3/4" 8-3/8" (21.2 cm)3" 9-1/2" (24.1 cm)All Cylinders are 9" length