Mid Cap is the term that is used to define a company’s market capitalisation. The S&P/ASX MidCap 50 is the index that represents the top 50 companies in the mid-cap space for Australia. Their market capitalisation generally ranges between $2 billion to $10 billion and includes the companies who are a part of the S&P/ASX 100 and does not include those in the S&P/ASX 50 and.