Ultra-Breathable Fabric:Our premium polyester cotton fabric allows optimal airflow,creating the ideal environment for yeast fermentation.The elastic edges ensure a secure fit for rising and aeration of your dough Universal Fit:Designed to fit jars with 3-4 inch mouths, making it perfect for various baking and fermentation needs Eco-Friendly & Reusable:Reduce waste with these washable,long-lasting fabric lids Effective Dust and Contaminant Barrier:The cover fits snugly over containers,preventing dust,hair,and other contaminants from falling into the dough,safeguarding the hygiene and quality of your baked goods Multi-Purpose Use:Ideal for sourdough starters,kombucha,kefir,cheese making,and more Get five covers in one pack, perfect for multiple jars or backups.