Opening Period in RTH (Regular Trading Hours) typically first 5 minutes defined as 9:30 am – 9:35 am.

Note: There can be various OPR time frames that traders use such as: 30 second, 3 min, 5 min and 15 minutes that are the most commonly used. Which one is best? It is up to the individual trader to do proper due diligent back tested comparative research to answer this question.