Soft & Airy: 100% Jersey Cotton Ely's & Co.'s Bassinet Sheet Sets are created from lightweight, soft and breathable fabric. Composed of 100% high quality Jersey knit cotton, our bassinet sheets offer cozy, welcoming environment for babies to rest their weary heads as they drift off into nourishing slumber. Adjustable Elasticity: Fits Multiple Mattress Sizes Ely's & Co's specially designed sheet set includes flexible, stretchable elastic, enabling a great fit and tight seal on all standard mattresses sold for Bassinet mattresses as well as Co-sleepers, enabling a great fit on irregular sized mattresses.