Flame Kings 20.3 Gallon propane cylinder is manufactured to ASME specifications in facilities that have a Quality Management System certified to ISO 9002 requirements. The advantage for ASME cylinder vs DOT is that they do not require recertification after 12 years from Date of Manufacture. This tank has a 16" diameter and is 27" in length. The distance in length from one set of holes to the other is just over 25". On each end there are 3 holes. Measuring from the center of the first hole they are spaced as follows: 0", 3.5", 6.5".