15 sts x 20 rows = 10 x 10 cm [4 x 4 inches] in stockinette stitch on 5.5 mm [US9] needles after wash and blocking
Circular needles: 5.5 mm [US9] / 60, 80 and/or 100 cm [24, 32 and/or 40 inches], 5 mm [US8] / 80 or 100 cm [32 or 40 inches] and 4.5 mm [US7] / 40 and 60 cm [16 and 24 inches]