The lab. We collected over 15 bucks over several years and only a handful were "good enough" to sort. The positive thing is you don't have to pay for a sort if they determine it is not good enough. Negative is that you put your buck through the stress of collecting to not get anything out of it. We used at least 4 different people to collect semen and the same results. The semen was good enough at collection to freeze conventionally but by the time it got to the lab (5 minutes) it was determined no good. We have Ai'd with sexed semen with good results but in my opinion needs some more work especially with the extender.