I'm showing this so you can see how well Clean and Boost dentin and enamel cleanser etches enamel.
The important thing here is to see how well Clean and Boost etched the enamel. Really I don't think there's any need for HPO3 etchant anymore. Just leave the Clean and Boost on for 20 seconds. Most of us are going to be using it to clean the prep anyway. Hope this helps.