I just posted the below info on Ralph's UFO 25 build thread. I'll re-post it here for posterity as it's a good reference spot.

I recently purchased some in the 3000, 4000 and 5000 series (and a couple in the 6000's). The last two are aimed at 15-25 size models and 25-32 size models, respectively. The 4010's look good for ailerons on the UFO 25 while the 5030's look good for elevator/rudder control with a 3010 for throttle. I will be using a very similar setup on another 30 size model.

Here are some pics of the various servos - unfortunately with no quarter for scale reference. Basically, they are micros (3000 - similar to HS65), larger micros (4000 - similar to HS82) and mini's (5000 - similar to HS225 although slightly smaller). The two 5000's look to be very good on paper, I will be trying them soon. They all come in specification pair sets with one having nylon gears and the other metal gears. The four 3000's series are geared for speed (3010, 3020) or torque (3030, 3040).

The last picture is of a 4000 servo which is the only analog servo in the micro/mini lineup. Specs are otherwise very similar to the digital 4010/4020 versions

David.