argentine boa x redtail is exactly what?

[Alexandra V]

It would be a BCI/BCO hybrid, exactly. If I remember correctly, BCO tend to stay just a touch smaller than a Columbian BCI, so expect something about the same size as a red tail (assuming it was a or Columbian BCI). If it was a smaller locality (Nicaraguan, etc.) Then expect it to be a little larger than the average "dwarf" BCI.