Does it work without an extension cord?

No. It is corded electric and needs an outdoor outlet plus a suitable extension cord. That gives constant power but limits how far you can work from the house.

Can it vacuum wet leaves?

It is built for dry leaves and light debris. Wet, matted leaves can clog the impeller and bag, so let them dry first.

How much does the mulching reduce leaves?

The mulching ratio is 12:1, so roughly twelve bags of loose leaves become about one bag of shredded material.

Is the backpack comfortable for long use?

The backpack spreads the 11.3 lbs across your shoulders, which most owners find easier than carrying a handheld unit, but it is still heavy for extended sessions.

What comes in the box?

The blower/vacuum unit, the backpack collection bag and the vacuum kit are included. An extension cord is not.

How does it compare with a cordless blower?

It has more sustained power and no battery limits, but a cordless blower is lighter and works anywhere. Choose this if you have an outlet and a lot of leaves.