The HopBlocker™is designed for use with pellet hops only. Whole loose hops will plug the unit. For using with whole hops, or a mix of whole and pellet hops, you need to bag your whole hops in a large muslin grain bag. This will not effect the utilization rate and will result in significantly less wort loss. Note that using small, fine-mesh nylon hop bags will reduce your hop utilization significantly. But the loose open nature of disposable muslin grain bags allow the wort to flow freely in and out of the bag, and utilization is not affected.