I use whole hops, 12-14 oz. in the boiler. I place the sliding part so it covers the large holes, using only the fine holes of the blocker. I never have blocked the fine screen. The hops surround the blocker and help filter the wort. The slider on mine doesn't fit real tight around the top part of the blocker, some wort flows through the large holes. I have had trouble with blocking when using 10-12 oz. of pellets, with whirlpooling as well as possible with the blocker in place and no hop bag. I use a hop rocket upstream of the plate chiller. Using a lot of pellets, the hops in the hop back would get plugged up. I run off 15-20 gallons of wort. With 5-10 gallon batches it probably wouldn't plug up. I am satisfied with the hop blocker and the hop rocket.