Emergency stop mushroom pushbutton for extension units, 22mm, round, red, plastic, latching, twist to release, no labeling, 2 break contacts, (including circuit board, contact module) Emergency stop mushroom pushbutton for extension units, 22mm, round, red, plastic, latching, twist to release, no labeling, 2 break contacts, (including circuit board, contact module) SIMATIC HMI PRO system components Emergency stop mushroom pushbutton for extension unit