There were two additions to the S&P 500 index unveiled on Friday -- Marvell Technology and Flex (formerly Flextronics) -- and that raises the question which companies could be next to gain admission into the highly desired index.

S&P Dow Jones Indices, which oversees the S&P 500, has a host of criteria including market value, domicile, profitability and corporate structure.

Bloom Energy, Astera Labs, Alnylam Pharmaceuticals, Heico, Rocket Cos. and Reddit look like potential additions because they are among the largest companies by market capitalization that meet the index's other criteria. The biggest companies not in the index stand the best chance of being admitted to the S&P 500. The minimum market value now is $22.7 billion for admission to the S&P 500.

Marvell Technology was by far the largest company by market value not in the S&P 500 index at over $200 billion when news came after the close of trading Friday that it would join the S&P 500 index later this month as part of a quarterly rebalancing. Flex was in the top 15 companies not in the index with a market value of more than $50 billion.

There are many companies with big market values traded in the U.S., however, that may not make the cut for various reasons. Southern Peru Copper is a South American miner that is nearly 90% owned by Grupo Mexico and Spotify Technology is domiciled outside the U.S. They are the two largest U.S.-listed companies by market value not in the index.

Other $50-plus billion market cap companies that don't make the cut now for the S&P 500 are Cloudflare and Snowflake because they aren't profitable based on generally accepted accounting principles in the latest quarter. Enterprise Products and Energy Transfer can't be admitted because they are limited partnerships.

What companies could be dropped next from the index following the news Friday that Campbell's, the soup and snacks company, and Pool would leave the S&P 500. They were two of the smallest companies by market capitalization, thus making them vulnerable to deletion.

Other companies with small market caps that could be dropped are Conagra Brands, Mosaic, Molson Coors and Builders FirstSource. They all weigh in at less than $8 billion.