The characteristics of knitting fabric waterproof for fitted sheet include:

1. Waterproof: The fabric is treated with a waterproof coating that makes it resistant to water and other liquids, protecting the mattress from spills and stains.

2. Breathable: Despite being waterproof, the fabric is designed to be breathable, allowing air to circulate and preventing heat buildup for a comfortable night's sleep.

3. Stretchy: The knitting construction of the fabric allows it to stretch and conform to the shape of the mattress, ensuring a snug and secure fit.

4. Soft and Comfortable: The fabric is typically made of high-quality materials such as polyester, which is soft and comfortable to the touch, providing a comfortable sleeping surface.

5. Easy to Clean: The fabric is easy to clean and maintain, as it can be machine washed and dried, and is resistant to shrinkage and wrinkles.

6. Durable: The fabric is designed to be durable and long-lasting, withstanding frequent washing and use without losing its waterproof and breathable properties.

Overall, knitting fabric waterproof for fitted sheet is a high-quality and versatile material that provides protection, comfort, and ease of maintenance, making it an ideal choice for use in bedrooms, hotels, and other settings.