For Mercruiser R/MR/ALPHA ONE 1983-1990 (s/n 6216687 – 0F386995) Long Length Trim Tab
Diameter: 3-1/2″
Height: 5″
Mounting Hole: 7/16″-10.
EMP Aluminum anodes conform to Mil-Spec A-24779(SH)

also crosses with:
Canada Metals CM34127A
GLM 12740
Reliance AMD-34127