3M™ Hookit™ Back-up Pad, 6 in, 5.16 in, 15 Hole, 50474 3M 50474 Hookit Back-up Pad 6" 5/8-11 Thread 15 Hole Different hole sizes equalise air flow thus providing best extraction. 3M 50474 Hookit Back-up Pad 6" 5/8-11 Thread 15 Hole.
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