Extra depth provides ultimate comfort, the quilted cover features internal walls to ensure the gently supportive filling stays in great shape and is always plump. The Silentnight Deep Sleep Ultimate Mattress Topper 500 is covered in a luxuriously soft quilted fabric for unmatched comfort. The topper provides gentle support and adds another layer of comfort to your existing mattress as well as helping to refresh and rejuvenate it. The Silentnight Ultimate Deep Sleep Mattress Topper. The topper is hypoallergenic which means it’s kind to skin and does not include any contents likely to cause allergies, it’s also machine washable so you can keep enjoying an ultimate deep sleep. Silentnight are the UK’s #1 sleep superbrand with over 70 years’ experience in creating products that offer solutions for every sleeper.