You guessed it. Regular insulin
which means that this type of insulin
works more like the kind that the human
body produces than it's counterpart Nph Insulin
Regular insulin is the fast acting type of insulin that is most active in the first two hours after injection. It's short period of activity makes it impossible to use alone. It pretty much has to be combined with Nph insulin.
When mixing R insulin with other types it is always the smaller ratio. High doses of it can be far more harmful than Nph insulin because the sudden reduction in blood sugar can cause fainting or at very worst induce a coma.
R Insulin is clear in the vial and should be destroyed if it starts looking cloudy like Nph.