D100 spools are 100 mm (3.94 in) across and hold about 0.9 to 1 kg (2 to 2.2 lb) of wire; D200 spools are 200 mm (7.87 in) and hold 5 kg (11 lb). K300 is the large industrial size at 15 kg (33.1 lb).
The machine’s wire compartment sets the limit physically. Buying 5 kg (11 lb) for a D100-only machine means decanting it, which is a poor use of an evening — check before ordering.
The questions welders ask
Is bigger always cheaper?
Per kilogram, yes, substantially. The counter-argument is corrosion: steel wire rusts once opened, and a 5 kg (11 lb) spool that takes three years to use will feed badly long before it runs out. Buy the size you will use within a year and keep it sealed.
Last reviewed 2026-08-14