Ziwi’s ZiPP technology allows hips and shoulders to settle deeper into the mattress than legs and back. Stretch sheets enable this settling with little to no restriction. Tight or non-stretch sheets restrict that settling and diminish the effectiveness of the bed.

Some specialty bedding sheets are already stretchy enough. If you think yours might be stretchy enough, you can test the stretchability of the fitted sheet by:

1. Remove all other bedding down to the fitted sheet.

2. Find where your hips would be if you were sleeping. With one hand, pull the fitted sheet fabric up away from the mattress.

3. Place your other other about six inches closer to the head of the bed and pull the fitted sheet fabric up from the mattress. Be sure the fabric between your hands is not loose.

4. Pull in opposite directions. If the fabric between your hands stretches at least another two inches, your sheet should be ok.

5. Repeat this stretch test again with your hands about six inches apart side to side. This allows you to test the stretchability head-to-foot AND side-to-side. 

6. You want to get at least two inches of stretch to ensure that your sheets can accommodate the contouring of a ZiPP bed.

7. If you aren't getting the minimum two inches of stretch, we recommend getting a stretchy protector to get the full benefit of our ZiPP technology.

Unfortunately no, since baggy sheets simply can't match the characteristics of stretchy sheets. While they may allow your hips to sink in at times, they can also twist and gather under your hips, creating a "bunch" point that inhibits settling. Or, they can bunch under your partner, leaving your side of the sheet too tight to achieve ideal settling.

Currently we are not planning to add any sizes other than the traditional bed sizes listed.