What direction do the fat ends go? Forward or rear on a flip kits?

I've search for pictures and answers and haven't been able to find a definitive answer.

Also what size are most people using on a flip kit on 4* or 6*?

 

it depends on which direction you need the pinion go go...they can be installed either way.

 

Most non flip kits I've seen the larger end faces the front of the vehicle and the skinny ends toward the rear of the truck. And most lifted trucks I have seen are the reverse, fat ends towards the rear of the truck. Also my truck is lowered 4.75" non flip kit and I have 8* shims in the truck and the fat end facing the front of the truck