All cylinders manufactured by Catalina Cylinders, have been and are being manufactured form aluminum alloy 6061, never aluminum alloy 6351.
Eddy current inspection of 6061 aluminum alloy cylinders at the time of the 5 year hydrostatic retest or annual visual inspection in the case of SCUBA cylinders is not required by the U.S. Department of Transportation (DOT) or the Canadian agency Transport Canada (TC).
Catalina Cylinders does not require eddy current inspection of the threads of their 6061 aluminum alloy cylinders.