Where does my Mattress Protector go? August 11, 2020 20:08 The Helix Mattress Protector fits snugly around your mattress, under your fitted sheet. Related articles Can I buy the Mattress Protector without buying a Helix Mattress? What does the Mattress Protector do? What is the Helix Mattress Protector? Can I wash my Helix Mattress Protector? How are the GlacioTex Waterproof Mattress Protector and GlacioTex Cooling Cover different?