Product review (5 stars): Great item for reduced dryer clearance.
This vent periscope works well and comes with clamps.  Another user complained that they needed to tape the seams.  I don't see this as a drawback as the seams for dryer vents should be taped.  I used "3M 3311 Foil Tape, 2" Width, 10 yd Length, Silver" which worked very well.
This periscope will collapse to as short as 2" OC offset without cutting as long as you have enough clearance above below the connections.  It would also be very easy to trim with a tinsnips.