chevy u joint problem?

[TBurrr]

so my u joint snapped the other day on my 95 chevy 1500 in doing so caused damage to the driveshaft and u joint retainers so i got a new drive shaft off same yr truck and bought some retainers but when tightend there is gap between the ujoint and the retainer i checked the size of the old u joint and its the same and i checked the size of the new retainers they are the same as well what is causing this gap or is this gap suppose to be there