This review was from Aug 14. To address the comment about it not fitting 4 inch lead, a large critter quitter will fit a standard 4 inch lead flashing, but you may have to shape it by hand or with the handle of a screwdriver. However, if the roofer was lazy and didn’t have a 4 inch flashing, they may have used a 5 inch flashing, in which case it wont go all the way down. An Xl unit will fit these. Here is the review
Easy to install and hopefully will prevent the squirrels from chewing on the vent pipes. Note if you already have lead sheaths over the vent pipes even the 4″ critter quitter might not be large enough to slip over the same.