ecofort Gtech Pro Manuel D'utilisation page 12

Bag Installation
Remove the lid by pulling gently upwards.
New bags have a tendency to sit flat when
first attached. Pull the bag down to sit
vertically.
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Fit the bag collar onto the tube underneath
the lid and push it up firmly.
To get maximum efficiency from the bag
it is important to expand the bag before
insertion.
Do not use the vacuum without a bag;
it may damage the motor and will
invalidate your warranty.