I fitted bearing buddies to a trailer. They fitted into the brake/wheel hub as push fit, not screw in. The original dust caps were prised out and the new buddies tapped in with a soft faced mallet.
The trailer originally had 203x40mm knott brake hubs with the buddies fitted as a factory option.
I replaced the Peak axle and brake assembly complete last year and the buddies were easily transferred to the new 200x50mm Knott brake hubs and were the same size push fit again.
I found a really useful feature was a 12-15mm diameter hole drilled through the wheel rim and through the brake hub (between 2 wheel studs) to allow me to flush the brakes with a hose pipe as soon as the trailer comes back out of the sea.
Those flushing points and the bearing buddies made the brakes and bearings last 12 years before I replaced the entire axle due to the rubber torsion bushes for the shock suspension getting hard and brittle.