Pretty much said the same thing but left the ultimate choice up to the user. The moment one suggests a specific servo the brand and type wars erupt. You can only lead them to the water...

If I had a JR radio I would use one of the 821's that came with the radio. Somewhere between $10.00 and $15.00. I normally use a JR 4721 nylon geared coreless servo but that's a lot more than most people want to pay. Once they get into the big leagues they start to understand the reasons for the higher end servos. Until then most are looking for the cheapest servo that will fill the need. A Hitec hs645 MG would be another acceptable choice in metal gear. Another Hitec mini that works for awhile is the hs225 MG. That one is as small as I would ever consider. For Futaba, Airtronics, and the other JR brand people will have to visit the servo sheets for those manufacturers to see what they have in standard sized, metal geared servos with at least 48 ounce inches of torque.