Mam ultivent but you do have to do them up properly but out of the avent, dr browns, tommee tippee and breast bottle i found my mam ones the best and they are great for keeping air out since i have just been using these jakobs colic has bisically gone he dosnt even need colic medicine anymore...they worked the same for myneice she swears by them...you can get them in blue or pink and 5 or 9 oz bottles..also dont waste ur money on the little bottles they r great for abiit but before you know it they will be on 5/6 oz n u will have to buy a new load of bigger bottles