1989 – Calvin Klein hired Berkowitz to join his menswear design studio. The Calvin Klein Men’s underwear line, which had launched in 1983, consisted of six basic styles. Berkowitz worked side by side with Klein for fifteen years, adding new designs and growing a $40M wholesale business to $500M.  

The designs Berkowitz created are still being manufactured by Calvin Klein and are considered brand icons, worn by millions of men globally: Boxer Briefs, Body Hip Briefs, Woven Boxer Shorts, Knit Boxer Shorts, and Lounge Pants.