The same technology is used in the Apple Watch Series 5 and later for its always-on display. The report notes that supplier LG Display will expand the production rate of its OLED panel factory lines dedicated to Apple. LG Display is planning to put in low-temperature polycrystalline oxide (LPTO) thin-film transistors (TFT) equipment that can add 25,000 substrates per month in monthly production rate into the lines by next year. The LTPO equipment being placed in the factory lines will be for OLED panel supply to ‌iPhone‌ next year, while the ones after May will likely be for panels for iPhones of 2022. Display analyst Ross Young thinks Apple's adoption of LTPO technology is a requirement before implementing ProMotion in its smartphone family. ProMotion allows for a variable screen refresh rate, from as low as 1Hz for static content to 24, 30, 60 and all the way up to 120Hz.