For best-in-class durability, PENN’s renowned CNC Gear technology features upgraded, ultra-strong stainless steel main and pinion gears. The Slammer IV DX’s Dura-Drag is also dually supported with an additional bearing incorporated in the spool compared to the standard Slammer IV. An exclusive silver and black cosmetic has also been incorporated across the range, along with a spare Hypalon handle knob for the ultimate in comfort on the water.
"They improved the sealing on the entire reel so water, salt and sand will not be an issue. This includes the line roller which now houses a hydrophobic bearing. It can be splashed or dunked and you can be confident your Penn Slammer IV DX Spinning Reel is going to keep on going!" ~JandHTackle 2022
Penn has added a 2500 size to this series. This smaller model features an HT-100 drag system. The 3500-8500DX use Penn's top of the line Dura Drag system that puts out a crazy amount of drag and has been refined so that you can access a wider range of drag based on your fishing situation. The reel comes with an aluminum ball handle and a spare EVA knob in the box.
Review: https://www.outdoorlife.com/gear/penn-slammer-iv-dx-review/