This filter was installed on a particularly nasty engine. Even after doing a strong citric acid flush twice, this engine persisted in dropping heavy material into the coolant. Only thing I could figure is that this engine must have enough "dead spots" in the coolant jackets that water flow through the block just can't hit them when flushing after a cleaning. In the future, we will be using a pulsating system to do the final flush. A lot of research indicates that the surging nature of a pulsating system overwhelms the flow area enough to blow out spots of dead flow in a cooling system. The engine here is a closed cooled marine engine that circulates engine coolant through its engine, as well as its exhaust manifolds. In order to assure maximum effectiveness of this system, the block drains and manifold drains were replaced with threaded nipples, all plumbed to the filter head, mounted below the level of the skirt of the block. Long story made short: Both lighter and heavier contaminates are left with nowhere to settle. Anything that seeks the lowest point in the cooling system finds its way being sucked toward the coolant filter. These nipples also create a flow path where there was not one before. The lowest points of the entire system are under suction. This is not a "bypass" course. Every single drop of coolant that goes through the drain nipples goes through the coolant filter. Period. The return from the coolant filter is also not a bypass. It is connected directly to the suction port of the circulation water pump (The one circulating engine coolant, not the raw water pump that sucks in sea water). This go around, the coolant remained free of contaminants. Clear, and no sediment in the coolant reservoir. The filter? In the last pic, you can see how absolutely pasted the filter media is. You can also see how clean the center tube is, even after contaminating it a little with my sad filter cutting and draining skills. Would have drained it by punching a hole in the bottom, but didn't want to lose any sediment, for maximum appreciation of the nastiness. In the future, I plan to use the block drains on both land and marine engines for coolant filter installs. Maybe drill out the restrictor cap for a little more flow. I've cut them out completely before to use them as full flow filters in heater core lines to protect heater cores, so they will flow a lot in modified full flow mode.