Premium style brass head nut standard 1/4" x 19 BSPP Engineered to deliver superior performance and reliability for long tail, short tail, surface drive style outboard mud motor shalf applications common on flat back canoe, gheenoe, john boats and small boats. Crafted with precision from high-quality brass; intrinsically high-strength and corrosion resistant material for best performance against harsh conditions and applications. Providing increased durability during install and use to prolong lifespan. Easy of install using outer tightening nut size of 13/16” or 21mm wrench. Model fitment varies.