The Patriots tight end Rob Gronkowski participates in the Buzz Off For Kids With Cancer event each year. Buzz for Kids is a Massachusetts based pediatric cancer charity.

According to

The One Mission Buzz Off is a fun and unforgettable event where passionate people come together to shave their heads in honor and support of kids with cancer; kids who don’t have the choice to lose their hair.  Just like a walk or road race, participants raise money by asking family and friends to sponsor their participation.

Source: Web Extra: Rob Gronkowski Shaves His Head For Charity