This Mr.Heater vertical vent kit meets all of the latest 2012 building heating codes for using category III venting and includes: 4" bird proof top; 4" vent support fire stop plate; 3" to 4" transition adapter; 4" roof flashing; 4" storm collar; 2-pcs single wall 4"x24"; 4" x 36" B-Vent; and 4" adjustable elbow.