Making and testing 6 inch diameter by 12 inch long concrete cylinders for compressive strength has been a primary means for quality control of plastic and hardened concrete. Traditionally these cylinders have been used to determine strength at specified ages. An AASHTO test method allows the use of 4 by 8 inch concrete cylinders when the nominal maximum size of coarse aggregate does not exceed 1 inch. The use of 4 by 8 inch cylinders offers many distinct advantages. Among them are: small cylinders are simpler to fabricate. A smaller rod, three-eighths of an inch in diameter and 12 inches long, is used; this makes the rodding procedure easier and less tiresome, especially when many cylinders are being fabricated. Small cylinders are easier to handle and transport. A 4 by 8 inch cylinder weighs about 9 pounds whereas a 6 by 12 inch cylinder weighs about 29 pounds. This lighter weight enables technician to pick up and carry one cured cylinder in each hand with little danger of back strain. Less storage space is required. Existing moist storage facilities will accommodate at least twice as many 4 inch cylinders as 6 inch cylinders. For laboratories with facilities that are becoming overcrowded, the switch to 4 inch cylinders might cancel out the need for expanding. Lastly, small cylinders are more economical. The purchase price of the smaller cylinder cans is 15 cents less per can than the 6 inch cylinders. There are a few disadvantages, however. Among them are: the 4 inch cylinders are limited to use when the nominal maximum size of coarse aggregate does not exceed 1 inch. In Arizona, this is only a slight disadvantage because most concrete in the state is made with aggregate meeting the minus 1 inch criterion. Also, small cylinders can be subject to misuse in the field. Because of their smaller size and lower weight there is more potential for damage from someone throwing them around or fabricating them improperly. However, this is easily prevented by close attention to proper fabricating techniques and by storing the cylinders in a safe place.