Kim Kardashian West has found her cosmetics soul mate.

On April 4, Kim and her longtime makeup artist, Mario Dedivanovic, took their friendship to a new level and officially launched the KKW Beauty x Mario line -- which goes on sale on April 5. To promote the line, the duo -- who've been friends for 10 years -- released a makeup tutorial in which Mario fittingly applies makeup to his "muse," Kim.

Mario called it "probably my favorite tutorial that I've ever done with her."

@makeupbymario / Instagram

In addition to 10 different eyeshadows, the KKWxMario palette features three lip products including a lipstick and two glosses.

The collection is inspired by all the looks that he and Kim have collaborated on over the years, and they've even named their shadows after memories, such as Vegas and Miami (two places where they've often been together) and Bronzey, because, Mario says, "there's no word we've said more over the past 10 years than 'bronzey.'"

He told Popsugar of the collaboration, "I basically pulled tons of our looks and our favorites and [picked] colors so that you can basically re-create any Kim-and-Mario look from the past 10 years."

Everything with this collection has meaning for Mario and Kim, including the April 5 on-sale date: It's the same day the duo met on a photo shoot back in 2008.

While Mario is a professional makeup artist, he wanted to design his products so that even the everyday user can feel comfortable with them.

"When I created the eyeshadow palette, I made sure that the products are very user-friendly and that you can apply a little bit and get the effect that you want, but you can also layer it and really get intensity," he told Popsugar. "But I also think about makeup artists who will know how to use and perfect it."

In the video, Kim added, "I think that's the basis of my brand, like, making things that are super user-friendly."

See the tutorial below: