What is the difference between nominal 2" and 2-1/8" OD sizes

it is specific to models requiring a -

Built with a high-grade fiberglass body for thermal stability and silica filler for superior arc quenching

and Tempstar air handlers and packaged units

By utilizing a calibrated silicon element

Carrier 0353101X44 Run Capacitor Els PW 17895 What is the difference betweenThe Carrier 0353101X44 Run Capacitor is a high reliability 2 MFD 440Vac component designed for precision performance in OEM HVAC replacement applications. Engineered for compatibility with specific Carrier, Bryant, and Payne air handlers and condensing units, this round run capacitor ensures stable voltage regulation for fan motors and small compressors. Its 440V rating provides a robust safety margin, allowing it to substitute for older 370V versions