Instructables
Picture of baby bottle cover
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here is a bottle cover for AVENT 125cc /4oz bottle.

you can use the idea with the modification you see to fit to other bottles

the base:
you do a circle
1- 5ch
2- 3ch as a dc then 1 dc till you reach 12 dcs
3- 3ch as a dc, 1dc in the same dc as joining, then 2 dc in each dc
4- same as 4

we will start to move up:

5-3ch as a dc, 1dc in the same dc as joining, then 1 dc in dc then 2 dc in dc and so on
6- 3ch as a dc, then 1 dc in each dc and before the end by 4 dcs we make 4 ch
7-same as 6
8- 3ch as a dc, skip dc and make dc in the next dc and before the end by 4 dcs we make 4 ch
9- 3ch as a dc, 1dc in the same dc as joining, then 2 dc in each dc and before the end by 4 dcs we make 4 ch
10- repeat 9 and 10
11- 3ch as a dc, then 1 dc in each dc and before the end by 4 dcs we make 4 ch
12- 3ch as a dc, then 1 dc in each dc and 4 dc in the whole ch
13- 3ch as a dc, skip dc and make dc in the next dc

and done!