rebuild kit wagner-lockheed.?

I got the rebuild kit, but there is one rubber-ring extra, there wasnt one in when the old stuff came out,

Question: where should the rubber ring be placed, I think
1-spring with aluminium vent-cap 2-rubber-cap 3-caliper, 4-rubber-ring 5- washer 6-snap-ring 7 rubber dust cap..

Is this correct?

greetings from Holland.