Sports Illustrated swimsuit model Kate Upton is busting out of her latest ad campaign and leaving little to the imagination.

The 21-year-old stunner showed off her curves once more in a sexy photo shoot for Choppers' summer campaign. In the new ad, Upton is seen flaunting her signature cleavage in a variety of low-cut tops.

She shared a snapshot from the shoot on her Twitter, writing: "I want to go back to Namibia.. So amazing there!"

The gorgeous gal isn't shy about flaunting her assets. Previously, Upton has posed in a bikini in the tropics before stripping down -- again, to a swimsuit -- in the sub-zero temperatures of Antarctica.

On Monday, photographers spotted the 21-year-old model while she was walking in New York -- and it appeared as though she decided to skip the makeup. The fresh-faced model completed her casual look by covering up her trademark curves in a loose-fitting gray shirt and pink skinny jeans.

The look was a far cry from the last time we saw Upton, a few days earlier, when she was in the Hamptons shooting for her upcoming film The Other Woman, wearing a tiny white bikini.

Directed by Nick Cassavetes, the comedy is due out on April 25 next year and tells the story of a woman who realises she is not her boyfriend's primary lover.

Cameron Diaz and Leslie Mann play the spurned duo who form an unlikely friendship as they team up to get revenge on the love rat who has been seeing a string of women as well as them.

Also making a splash is Nicki Minaj, who plays Cameron's opinionated assistant at her New York law firm.