For the first time since Apple began selling its iPhone 6S and 6S Plus models, investors will find out just how well they resonated with consumers.
Apple, which reports its fiscal-fourth quarter earnings after Tuesday's market close, unveiled its new generation of iPhones in September.
iPhone sales guidance will be key, according to Credit Suisse Managing Director Kulbinder Garcha.
"Can the iPhone business continue to grow? We think it can," Garcha told "Fast Money". "We're looking for 78 million iPhones to be sold in the December quarter."
Garcha, who has an "outperform" rating and $145 price target on Apple, is also looking for 39.5 percent in gross margins going forward.
China will be another major factor for Apple.
"Investors will be playing close attention to how the Chinese businesses fared especially because it was growing so strongly in the first half of the year," said Garcha, whose estimates are a hair lower than Wall Street forecasts.