The William Mitchell square cut pen set
are for right-handed calligraphers..

The card set consists of 10 nibs of assorted sizes [ 0, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6 ] and 2 x slip-on reservoirs.
Mitchell Reservoirs - these slide on under the nib for the Mitchell Round Hand Nibs. You may need to adjust them slightly, but this is no problem as the metal bends easily.

Round Hand Nibs Sizes: 0 (3.3mm), 1 (3mm), 1-1/2 (2.5mm), 2 (2.3mm), 2-1/2 (1.8mm), 3 (1.4mm), 3-1/2 (1mm), 4 (0.9mm), 5 (.75mm), 5.5 (.675mm), 6 (.6mm). Flexible calligraphy nibs from England.
Reservoirs are purchased separately also. Though they are called Round Hand, these chisel edge nibs are good for many alphabets including Italic, Carolingian, Uncials, Gothic (Blackletter/Old English), Foundational Hand, and Roman Caps. Widely used by professional calligraphers with and without the reservoirs.

Quote product reference: M00188