CET emitters are fully etched to have a consistent thin-walled capillary extending to the tip. As they are constant ID, they are resistant to clogging and give very high sensitivity signals at low flow rates.
PET emitters are pulled to a specific 8um tip and etched to form a long thin-walled tip capillary wall leading up to the tip. These can give even higher sensitivity for very low flow rates but are slightly more subject to clogging if trace particulates or debris are in the sample stream.

