The Monitor Unit: A small plastic box with an electronic digital screen (LCD or LED) and control buttons.The Cuff: A fabric band that wraps around your upper arm or wrist. It contains an inflatable rubber bladder.The Air Tube: A flexible plastic hose that connects the cuff to the main monitor unit. (Some wrist models combine everything into one single unit without a separate tube).Power Source: Operates on batteries (like AA or AAA) or an electric plug-in adapter.