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The main difference is that Carabiniers had epaulettes as they were considered the grenadiers of the Cavalry and the horse grenadiers did not have epaulettes. Aiguiette on the right and contre epaulette on the left. A bit of trimming will be necessary
Emir Bhukari gives the top of the cap as a cross rather than a grenade - which was also on the top of the carabineers cap. The carabineers did not have scale chinstraps where the HGrens did.
The epaulettes on the carabineers will need to be trimmed down, to just shoulder straps, aiguillettes will need painted on and the pockets on the carabineers are horizontal where as the horse grens were vertical.