The "park" number is an old carry over from different classes of BRUSHED motors that pre-dated BRUSHLESS for rc use. When brushless came along and grew in popularity some particular classes of motors retained the "park" nomenclature so old schoolers would know what to buy without much guess work. Unfortunately there is hardly any common standard for classifying brushless motors. Best practice is to note the watts and kv of a given motor for your application. So read the specs, don't get hung up on names.....there's a whole other naming system to compare brushless to gassers but I don't want to throw too much at you.