Kolos romper is worked from the bottom up. First, the front crotch gusset is worked, then, the back crotch gusset. Both pieces are joined in the round, then, the body is worked. Next, the back part is worked, followed by the straps. The front part and leg opening edges are worked last.

Sizes: 0-3 months, 3-6 months, 6-12 months, 12-18 months.

Yarn: cotton yarn with a yardage of approx. 165 m/50 g (180 yds/1.75 oz).
Possible substitutions: cotton, merino wool or blends with matching gauge with 4 mm (US6) needles.

Recommended yarn: Drops Uni Color, YarnArt Jeans, Alize Cotton baby soft, Sandnes Garn duo, Drops Safran, Gazzal baby cotton.

Totals used: 60 (80) 100 (120) g (2.1 (2.8) 3.5 (4.2)) oz.

Needles: circular needles 3.5 mm (US4) and 4 mm (US6) with cable length 40 cm (16 in).
Notions: 4 mm (US6) additional needle, crochet hook, tapestry needle, markers, scissors, about 1 yard of contrasting color waste yarn, 5 buttons with diameter approx. 1-1.5 cm (0.4-0.5 in).

Make a gauge swatch and count your stitches after washing and blocking. It might be necessary to change needle size to achieve a matching gauge. If you knit tighter (have more stitches), use thicker needles, if you knit more loosely (have fewer stitches), use thinner needles.
Approx. 24 sts and 36 rows = 10 x 10 cm (4 x 4 in) in pattern on 4 mm (US6) needles (after washing and blocking).