The design success is simple
It's all because of the curved hem.
(U.S. patent #5,628,077 )

The Cinch Sheet holds virtually wrinkle free and smooth under the discriminating sleeper. No elastic to break down and fail. No compromises to wildly varying mattress thickness. The performance is unmatched. This sheet will create a new standard in performance and comfort. This sheet fits all mattresses from 8" to over 15"!

The cord lock located at edge of mattress for easy access to tighten or release sheet.

Fits any mattress thickness!
Gather panels at the corners provide broad adjustment capability. The design in this area provides material take-up without binding the drawstring.
Simple theory: Like a bridge
The edge shape of the Cinch Sheet is the key to the success of the sheet.

On a suspension bridge, the main cable is deliberately curved to evenly distribute support along the span length. This same principal is the key to the "Cinch Sheet" drawstring sheet. The hem is curved in the same fashion to distribute the force from the drawstring along the full length of the edge of the sheet. This is how the "Chinch Sheet" drawstring sheet achieves its exceptionally intimate fit to the mattress.
bridge.JPG (15869 bytes)
The Special hands free cord lock makes tightening easy.
(patent pending)

To tighten the cord, pull outward on the loose ends. The locking tab automatically locks when the ends are released. To loosen sheet, pull the loop on the locking tab and the cordlock releases the cord. See the demo video:
DEMO LINK
THAT'S A TIGHT SHEET!
Results:

Drawstring Sheets are far more comfortable than any other sheet.

The result is a very tight, flat sheet that is very comfortable to sleep on. The slick feeling under your body is unmatched by any other sheet.

From the first night until they are changed, the Chinch Sheet drawstring sheet has that just made feeling, night after night.