The Bottle Pump is a portable pump that can be placed in any bag or even a cup holder. It has a needle that has a rubber pump lining that will fit into bottle cap opening to prevent the eascape of air. The Bottle Pumps needle can be removed from its socket to make a bike pump. The air opening above the air pump opening is for air to come into the pump. The handle is about the length of the average human hand and so that your hand can fit snugly onto the handle for maximum pumping efficiency. The cylindrical wall-like piece of plastic  is airtight so no air can escape the pump.