Aramid fibres (Kevlar), claims to be stronger than steel 🤷🏻 I had one for my iPhone X, survived being dropped down the stairs several times, into the bath and from the loft bouncing off a metal ladder with only minor scuffs than cleaned away. Doesn’t claim to be anything other than a tactile case that’s ultra slim; but I’ve only ever had to replace screen protectors after 4 years of use. Only visible damage on the 5 year old phone is some scratches on the glass edge above the notch.