【EXCELLENT COMPATIBILITY】 the lid can replace 30 ounces (the inner diameter of the cup is about 3.74 in) insulated stainless steel cups of any material, but it is not suitable for RTIC flat-bottomed cups! In order to avoid you to buy an inappropriate size lid, before buying Please measure the inner diameter and outer diameter of the cup, and then please refer to our size pictures. These pictures are our actual measurement. And check the details of our description. 【SAFE MATERIAL】 Made of top food grade crystal clear AS plastic which is BPA free,Eco-friendly, Sturdy and durable Non-toxic & dishwasher safe. 【SPLASH-PROOF】 The edge of the flat-bottomed cup lid is lined with a silicone gasket to prevent splashes and major spills when the cup is turned over. There is an air hole on the top of the slider, through the air ergonomics, which helps to reduce splashing. However, this cup lid cannot be guaranteed to be 100% leak-proof. Please check the two precautions described below before purchasing.(Please note that the hole cover most can accommodate straws diameter about 0.8 mm ) 【EASY TO USE】 this replacement tumbler lid is designed with a sliding button, easy to slide and can be closed or opened with one hand, practical and easy to carry, which can be applied in many life scenes and is an ideal life assistant.