Frequently Asked Questions
L3Harris uses a set of codes to indicate the minimum and maximum (in some cases) specs that a tube will have.
The first letter is the Restriction Indicator. The letter will either be an L or U. L indicates it is a Limited tube, which has maximum spec restrictions. L tubes are meant for export to other countries by qualified exporters. U indicates it is an Unlimited tube, which does not have maximum spec restrictions. U tubes are meant for domestic use.
The second letter is the Image Quality Indicator. The A indicator is for aviation tubes that have more stringent minimum cosmetic spec standards. The M indicator is for ground use tubes which have less stringent minimum cosmetic spec standards.