Rule 11 of Central Excise Rule, 2002 provides that the Invoice should also contain the Description and Classification of the finished excisable goods to be removed from a facotry or warehouse on payment of duty . Hence so long as the Description of the goods is properly mentioned and quantity shown in either Metre or Kg as well as proper duty payment made, then there is no bar in gererating invoice in both Unit for different buyers. Provided both the Unit (Metre & Kg) are also separately shown in the RG1 Register and intimated to the JAC/JDC.
However,if assessee desires to keep different sets of invoices for different classes of buyers, then permission would be required to be taken, along with written intimation from the JAC/ JDC.