The energy efficiency class of this bulb is F. Since this bulb has the quite common E27 socket, it will fit in many light fixtures.
From Argos
Osram Vintage 1906 Caged 4W LED Warm White Edison Bulb
OnBuy
Osram Vintage 1906 LED, Retro Design, in Filament Style, Edison Bulb shape: E27, Clear, Warm White, 4 W, Pack of 1
Roov
Osram LV962095 1906 LED 37W Vintage Filament Gold Glass Edison ES Bulb