Comparison : Item # 73151-1/2 & 3/4, 4 11/16" Square Extension Rings with Concentric Knockouts
Item # 73171-1/2 & 3/4, 4 11/16" Square Extension Rings with Concentric Knockouts
Item # 73171-3/4 & 1, 4 11/16" Square Extension Rings with Concentric Knockouts
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