From the manufacturer: "First introduced and offered for sale in 1998, the DILE Insert Foreskin Restoration System is an internal packing device which can be adjusted (incrementally) to expand longitudinally once it is inserted and enclosed within the developing foreskin. The DILE Insert can be used in conjunction with a modified t-tape or a silicone retainer (i.e., tapeless) as well as with or without a strap. The "dual-action" of the DILE comes from the fact that when "pulled" the DILE provides tension on the outer and inner skin (like normal tugging), however, when expanded, the DILE provides for the extra "push" of tension on the inner skin."
What is here referred to as "expansion" is what today is known as dual tension. The DILE was the first dual tension device.