The Yankees and Mets are wearing first responders' hats today for

Baseball cap history and timeline

Mike Piazza suggests 9/11 national remembrance

SportsCenter - Both New York baseball teams, the New York

MLB Players to Wear Ribbons on Caps for 9-11 – SportsLogos.Net News

Best Mets and Yankees hats, jerseys, gear for the Subway Series

Mets will wear special uniforms to mark 9/11 anniversary

Mets, Braves wear caps to honor first responders

Yankees, Mets get green light from MLB to wear first-responder caps on 9/11 anniversary

Mets' John Franco continues to pay tribute to 9/11 first responders

Yankees, Mets finally get to mark 9/11 anniversary with commemorative caps in-game

Jonathan Villar #1 - Autographed Game Used First Responder Hat and Game Used White Commemorative Jersey with American Flag Patch - Mets vs. Yankees - 9/11/2021

MLB finally gives Mets permission to wear NYPD, FDNY hats on anniversary of 9/11

Dominic Smith #2 - Autographed Game Used First Responder Hat and Game Used White Commemorative Jersey with American Flag Patch - Mets vs. Yankees - 9/11/2021