Changes in Lot Size

Can different lot sizes co-exist in the same month?

Yes. For instance, in the past lot size revision which happened in January 2025, weekly contracts like NIFTY-OPT- 2nd January 2025 had the lot size of 75 (revised) while for monthly contracts of 30th January , 2025 the lot size remained 25 as it was introduced before 21st november, 2024.