This is a great bearing to use in salt water since it is stainless steel and therefore will not rust. This bearing measures 2.441 inches at its base. It is designed to be used in most 6 bolt hubs.Bearing put a small amount internal pressure in the hub (about 3psi).Universal for trailers prevent wheel bearing failure on boat, RV, snowmobile, ATV and utility trailers. When the hub is submerged water cannot enter the hub because of this pressure. Made of high quality stainless steel with maximum anti-corrosion ability, keep water, dirt or road grime out of wheel hubs and bearings.Its a great way to extend bearing life and service your bearings in-between hub re-packs. its help keep dirt and water out of your hubs and bearings.If your trailer is often in a saltwater environment or needs to be driven on the highway for a longer period of time, then this trailer partner bearing protector is vital for the bearings.