This is the louver that installed on the right & left sides of the Ford under-dash hang-down evaporator unit, as used in the 1965 Mustang.
It installs between the upper and lower case halves.
Hard to find part.
Two required per underdash unit.
This is the larger 80mm version, the smaller 50mm version is also available see part # 02-106
Sold individually.
