2 different recipes. Brands sell different pigment mixtures under this name, so they won't all look or mix alike. Compare the pigments below.
Who makes it
PR101 Red Iron Oxide1
- Rembrandt Artists' Oil Colour No. 803PW6 PR101LF I Semi-opaqueSeries 315 ml tube · 40 ml tube · 60 ml tube* · 150 ml tube*About Rembrandt
Sizes are the ones each line is sold in; marks a size only some colors come in. Check the store for a particular color.