Foreo ISSA Hybrid Wave Brush Head with Medical-Grade Silicone + PBT Polymer - Black. This ultra-hygienic brush head is designed for effective plaque removal and gentle gum care. It features a hybrid of silicone and PBT polymer bristles, combining durability for heavier plaque buildup with softness for sensitive gums. Each brush head is designed to last for 6 months and can be used with any ISSA or ISSA mini toothbrush.