The index of the top 40 shares reflects market capitalisation and liquidity. Cucinelli has risen 18% this year for a valuation of some 5.5 billion euros ($6.1 billion).
Best known for its cashmere clothing, Cucinelli said last month that its sales had risen by a third in the first three months of the year. It has also been boosted by the general buzz around luxury goods stocks, the traders noted.
ERG shares have by contrast slipped this year and the company is worth only around 4.3 billion euros.
There is one more hurdle to clear to claim inclusion in the index as the newcomer has to rank 36th or above in terms of valuation. Cucinelli is currently vying with truck and bus maker Iveco for that spot ahead of the May 31 review.
The index changes take effect from June 19.
($1 = 0.9084 euros)
(Reporting by Giancarlo Navach, editing by Gianluca Semeraro and Keith Weir)
