What are the special stocks in SAP? | SAP-MM

 Special stocks are defined as the stocks that must be managed separately by a company. They car be either company owned or external stocks.
They can be categorized as:
=>    Consignment
=>    Subcontracting
=>    Stock transfer using stock transport order
=>    Third-party processing
=>   Returnable transport packaging
=>    Pipeline handling
=>   Sales order stock
=>    Project stock.