A Why should I invest in heavy duty dock mounted bumpers instead of traditional hanging fenders? Heavy duty dock mounted bumpers provide secure, always-in-place protection without the risk of shifting or sagging like hanging fenders. Slammer Marine’s dock bumpers are foam-filled (not air-filled), meaning they absorb impact rather than bounce your boat back into harm’s way. They are designed to handle strong forces, making them ideal for high-traffic docks, windy conditions, or boaters who desire peace of mind knowing Slammer Marine is always alongside and always on station.