These
Retube Kits are for the 50 Watt Marshall 900 / 4500 series Amps including the 4500, 4501 and 4502 models using 5881 power tubes.
A very small number of the 4500 series amps produced from 1990 thru 1991 used EL34's. If your 4500 series Marshall came with EL34's or the amp has been modded to use EL34's (Screen grid resistors & bias resistor swap) then please use the kits for the 2500 series amps.
The last option allows you to fully customize a kit exactly the way you want!