Exchange Market Size (EMS)
Under the PLUS Trading Rules for MiFID, PLUS requires each market maker registered in a PLUS security to display a two-way quote in a minimum size known as the Exchange Market Size ("EMS") which is firm to an enquiring broker.
To find the minimum requirement, as specified by PLUS, for securities such as FTSE 100, FTSE 250 liquid, FTSE 250 non-liquid, FTSE Small-cap, FTSE Fledgling, and AIM among others, please download the EMS document
here