Exactly what I use on my 1952 Riley. Really excellent considering the reflectors are over 60 years old.I have tried some oftenly praised ones in my Range Rover P38.
They do look super bright when looking at them. Driving at night was a nightmare, felt like using a forties 6 V system. And yes they had af fine thread and ring for focus adjustments.
Went for quartz halogen "nightbreakers" best bulbs ever.
That said I am sure there will be even more progress with led lights. But I was very disappointed.