Reference Zinc Reference cell for Electro Guard Corrosion system 1/2" trough hole with 1" counter bore Type Thickness Width Length Weight REF-1 5/8" 1 5/8" 2 7/8" .520 REF-2 5/8" 2 1/8" 4" 1.000 REF-3 5/8" 2 5/16" 6 1/2" 2.120