Product review (5 stars): Best Dryer Vent Duct Kit I've Ever Seen.
When I had my dryer installed in my new home, I had purchased a metal duct kit like this one for the installation, but the installers said they could not make it work, and so they used a plastic duct.  I learned later that plastic ducts are a fire hazard.

2 years later, when I pulled the dryer out to replace the heating element, I found a plastic duct that had been crimped and kinked and was laying on the floor fully extended, causing far more length and restriction than required.

I decided that I would figure out a way to make the shortest duct possible, with the least bends and restrictions possible.  I found this kit on Amazon and ordered it.

The kit comes with two elbows, 4 clamps, a length of metal duct, metallic tape, and instructions.  In short, everything you need to make the best duct possible for almost any install.

For my install, I cut the metal duct in half with a utility knife, then installed one elbow on the exhaust of the dryer.  I installed the shortened metal duct to the other end of the elbow, and then ran the duct straight up to the house exhaust duct.  That duct aimed at the floor, and so needed no bend.  It took some contortions to do it, but I was successful.

Now, instead of having 6 feet of kinked plastic duct, full of lint and a fire hazard, I have a metal elbow with 2 feet of metal duct going straight up to the house duct.  Their is a big difference now in the amount of exhaust flow.  You can hear and feel the increased flow.  Drying times were cut by about 25%, and should result in 25% less electricity used as well, by the dryer.  This kit should pay for itself in a month or two, and is also much less likely to cause a fire, like a plastic duct can cause.  That feature is priceless.