'Love & Hip Hop' Sex Tape Stars We Get Off on Measuring

4/18/2014 7:30 AM PDT

Mimi Faust and Nikko Smith -- stars of the "Love & Hip Hop" sex tape -- have a bit of an unusual fetish ... and it involves a ruler. We'll explain ... 

According to sources who've seen the tape in its entirety, there is a scene where Faust measures Smith's flaccid penis with a ruler. She then says, "Let's see if we can make it grow." You can guess what happens next. 

Our photog found the couple at LAX yesterday ... where they joked about popularizing a certain shower rod ... and explained why they're so into the measuring routine.

BTW ... we'll spare you the exact numbers, but it's obvious why Smith's into logging his stats.