 
 <prompt> ```Why these elevators fit carry only 525 pounds? Based on the question wey dey above, write a context wey go contain the answer. E fit be 1 - 20 sentences. Context:``` <response>: ```One elevator wey be like dis dey use vacuum on top of the cab and valve on top of the "shaft" to move the cab up and close the valve to keep the cab for the same level. Dem dey use diaphragm or piston as "brake" if pressure sudden pass for top of the cab. But to go down, e dey open the valve make air pressurize the top of the "shaft", make the cab fit go down by im weight. E mean say if power fail, the cab go automatically go down. The "shaft" dey make of acrylic, e dey always round because of the shape of the vacuum pump turbine. To keep air inside the cab, dem dey use rubber seals. Because of technical wahala, these elevators get low capacity. Dem dey usually allow 1-3 passengers and up to 525 lbs.``` 