Here you will find all refills for your Montblanc Rollerball. Make sure you order the right refills! Do you still have an old refill? Then read what it says on the refill.

Does it say 'LeGrand Rollerball Refill' on the old refill, then you have a Montblanc rollerball in a larger version and so you specifically need the LeGrand refills for this. If it says 'Rollerball Refill' on the old refill, then these are the 'normal' rollerball refills from Montblanc.