Product review (4 stars): A good design, with some flaws
This is the second floating dryer vent cap that I have purchased.  The first had a hinged cap with a catch and the plastic in the hinge broke, rendering the unit useless.  The design of this product seems more sensible, with the cap just fitting down over the vent.  Both the floating vent caps that I have tried do an excellent job of keeping animals and cold air out of your dryer outlet hoses, although their bulkiness makes them less than unobtrusive on the side of your house.

Note added 3 months later: Unlike the previous floating cap vent I had, this unit does not trap any of the "bleed-through lint" that gets past the dryer filter and instead, blows it all over my deck where it has made a HUGE mess.  I revise my evaulation to 3 stars.