2600: Stainless slotted 1/4 turn fastener – plus flush. If total panel thickness is near top of range -next greater size is recommended. 2700: Stainless slotted 1/4 turn fastener -flush. The dash 5 and greater stud assembly requires retaining rings., dash 4 and smaller are self-retaining. Solid rings hold stud assembly stationary to top panel. Split rings allow stud assembly to move freely within the top panel. If total panel thickness is near top of range -next greater size is recommended.