This is really a very useful indicator for price action traders who are watching the key areas for potentially high probable trade setups. This script can be applied to see the pre-market highs and lows for stocks, also today's high/lows, yesterday's highs/lows and after hours highs/lows too.
You also have the option to turn on/off the highs/lows in the settings.
First, I like this indicator. However the pre-market levels are not accurate on some instruments. I've noticed in some cases it marks the pre-market H/L after the market opens, sometimes as late as 10:30.