COB stands for Chip on Board LEDs, basically it is a big yellow led chip which has no pattern and hence not apt for headlights as there will be no focus and Pattern. It will blind others with the glare
CSP LED stands for Chip Scale Package, ZES is similar to CSP and looks nearly identical. These chips mimic the Filament of a Normal Halogen bulb and hence reproduce the stock beam pattern well and don't end up blinding on coming traffic.
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COB Led
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You can clearly see the difference between COB and CSP/ZES