All current models feature robust sapphire crystals.
Past models used acrylic crystal -- a nod to vintage watchmaking. Acrylic crystals perform best when kept away from chemicals and alcohol, including sunscreen and sprays, which can weaken the crystal over time.
For cleaning regardless of crystal type, use water and a microfiber cloth only.
For scratches on acrylic, Polywatch works well. Do not use any other chemicals on acrylic crystals. A how-to guide for using Polywatch is available at lorierwatches.com/pages/care.