Pictured are the mono-leaf on the left and multi-leaf on the right. The difference is the depth of the pocket. 


If you are making your own housing these may be of help. They fit a 3" tube stock diameter. 


These perches are common on the following:


1967 Camaro - Mono-leaf

1968-1969 Camaro Multi-leaf

1970-1981 Camaro Multi-leaf

1962-1967 Chevy II Nova Mono-leaf

Mono or Multi Leaf Perches - 1 pair