Purchased these ear plugs at a local Wal*Green pharmacy to use at a confrence my husband and I were attending.
My son is 2.5 months old and these worked wonders, we were 50 feet away from the speakers and he slept the majority of the time.
Individually the ear plugs were a bit big and if he rubbed his head on the car seat head rest he could dislodge them.
I ended up using 1/2-2/3 of an ear plug in each ear and it worked much better. They stayed in and he could not 'rub' them out of his ears. I used them on the average of 4 times a day for 3 days before I needed to use a new set.
My son did not like when we initially put the ear plugs in his ears. We found if we put the ear plugs in about 10 minutes before the music started, and push him around in the stroller he would get use to the ear plugs and go to sleep.
My friend used them on her 6 month old, but the baby kept pulling them out of her ears.
If you are using these on an older infant/child I would recommend purchasing the headband to keep their fingers away from them.