This O-ring is located on the upper and lower pistons of the brew group in the WMF automatic coffee machines listed below.
1x o-ring/gasket as shown
WMF
800
1300
1400
2000S
Schaerer
Coffee Factory
Coffee Joy
Coffee Prime
Coffee Vito
Opal
Siena 1
Solis
Master Pro
Master Top
Ultra One Touch Cappuccino
Panasonic
NC-ZA1YNQ
Dr.Coffee
F2
F10
F11