This is a (standard-sized) 2-1/4-inch pinback button as shown. NOTE: This is a popular design, BUT we would recommend not going berserk ordering lots of them right out of the gate, because at actual button size it's not easy to tell that that is a photo of Bernie with a bullhorn! So we would recommend that you go easy on your quantity this design until you've seen it in person to decide for yourself about that.
I Wrote the Damn Bill (211e)
...on the button's "curl" (either upper or lower edge, just outside the face of the button that's visible when it's viewed from the front). In 2016, for purposes of selling buttons at Dem-Party-sponsored events, this was usually* considered an acceptable alternative to having a union "bug" on the button. Hopefully this will continue to be the case in 2019 and 2020 (although as devoted as the Dems are to suppressing/silencing us Bernie folks, who can say??!).
* Of course, in the final analysis it depended on the personality of the event organizer. But most of them eventually concluded that, in the absence of a volunteers' union (LOL), they'd concede the validity of LABOR DONATED as an option.