Speedtrak radar - SpeedTrac X Radar Gun Hands-Free Speed Gun X-treme

it definately knows when you are serving faster or slower, but this varies according to the direction of the serve. also, it records probably some 20-30 mph slower than actual. good for training, but definately not accurate.
Pros: easy to set up
Cons: not calibrated

This review was written in the old system and had content requirements that are different than reviews written today.