From the appreance, brass wheel caster and zinc alloy wheel caster are same. Even for short time usage you can not tell the difference. But with the time on, you will find that zinc alloy wheel caster is easily broken. It can not bear the heavy furniture weight. While brass wheel caster is more firm as time goes on. Brass wheel caster does not change for long time. Compared brass wheel caster, zinc alloy wheel caster is much cheaper. But we only make brass wheel caster, as we hope customers get the best quality.