For those looking for 603 motors that are a little less powerful than the 19000kv Jiffy Juice motors for indoor flying and particularly racing, Scoot Juice is an awesome option.
These motors offer more throttle resolution, similar to brushed builds you may be used to, but with all the control and authority of brushless motors. They are only slightly faster than the Smooth Juice motors, which come in at 15000kv, so picking which motor is right for you depends on what kind of top speed you want to acquire at the sacrafice of throttle resolution. In short, the slower your motor the more control you have over the exact speed and thrust you're putting out. 603 16,000kv motors have been a standard since long before Tiny Whoop Brushless motors came out, but now use a C-clip to help motors last a lot longer and are much less likely to suffer from bell-slippage after heavy crashes.
These motors have a 1mm shaft size, so make sure you have 1mm shaft props!!