INTRODUCING: Defender D4 Stainless Steel Casters Introducing the Defender D4 Series, our strongest and latest advancement in 2″ wide stainless steel kingpin casters. Featuring a robust 3/4″ kingpin construction, Defender D4 rigs outlasted traditional 5/8″ kingpin rigs by up to 2x in internal durability testing—making the Defender D4 your best protection in corrosive environments! The D4…