what gearbox?

what gearbox? seen threads saying to use an 020 gearbox in a 2l 16v conversion?? why this box and whats it normally in? thanks for any input

020 is the general gearbox type, as found in 1.5-1.8 Mk1 Mk2 and most Mk3 Golfs, Scirocco, Jetta, etc