COMPATIBLE with Avent and Spectra S1/ S2 widemouth flanges to use with standard sized bottles. Compatible with Medela, Ameda Narrow Baby Bottles. Note: not compatible with wide mouth Dr. brown bottle, not compatible with lansinoh bottle, not compatible with Avent bottle, not for glass bottle. LEAK-PROOF - NO LEAKS BETWEEN THREADS, just screw it onto your narrow neck bottles, and attach it directly to your wide neck flanges. EASY TO CLEAN - You just need a bottle brush, soap, and water that can remove the dirt in your adapter. SAFE MATERIAL - Made with Food Grade PP, Dishwasher top rack safe. Can be clean in water steam or boiling water. Pump Directly into Baby Bottles Ideal for Spectra S1/S2 wide-mouth flanges to pump directly into standard-sized compatible with Medela pump bottles.