MLS and Adidas have sponsorship deal..​ Beckham has a lifetime contract with Adidas. 

Since the Mas brothers joined the team in Dec. '17, I chose their company as the sponsor

Primary Kit

The light gold anchor pattern symbolizes that the MLS is here to stay in Miami. Combined with the white jersey and blue stripes, I wanted people to see it and think ‘majestic’. ​​ 
Secondary Kit

Like a lot of things you see in Miami, I wanted this jersey to shock people, but in a great way. Waves across a jersey have never been done before, the Legacy stands for the beginning of a new era.