The lot size of 40 F&O contracts is being reduced from May 2021 expiry onwards. The date of the revision in lot size is April 30th, 2021. Until April 29th, the May & June contracts will trade with the present lot size. The F&O contracts for April will continue to trade with the existing lot size till expiry.
You can check the list of stocks, their present market lot, and the revised market lot below: