Well, as always, there's the best and there's not too expensive, and these two rarely meet.
I bought 2 sets of PrincessAuto muffs when they were on sale for $7ea. One set stopped working the very 1st time, the other one a few weeks later. When it did work, the delay in restoring sound amplification after a shot was very long, so if you or someone fired many shots 3-4 seconds apart you'd hear nothing. YMMV.
I then ordered 2 sets of 'Howard Leight Impact Sport' from envirosafetyproducts dot com in the US. Cost me $47.68US each plus $24.75 for USPS Priority mail, i.e. $120.11US in total. Me and my older son love these, my younger one cannot use them - they don't curve quite right behind his ears, i.e. they do not touch his scull thus creating an opening. Go figure... Well, two out of three ain't bad. BTW, my kids are grown-ups, I don't know if these would fit youngsters at all.
These Impact Sports are slim - which is an advantage for trap shooting, they let you put your cheek down properly. Still, we double up with foam earplugs when shooting indoors.
Both sets are still on their 1st set of batteries - that's 1.5yrs of (almost) weekly use.
Highly recommended...