Needles
24" (60 cm) circular or straight needles. US 7 (4.50mm) for last row and BO to avoid flaring. US 8 (5.00 mm) for body.
Gauge
One cable pattern repeat (16 stitches x 8 rows), blocked =2.26" x 1” (5.75 x 2.50 cm).
Garter slip stitch pattern (17 stitches x 34 rows), blocked = 4” x 4” (10 x 10 cm).
Note - It's highly recommended to do a gauge swatch of the garter/slip stitch pattern to ensure that your needle size gives you enough drape in the fabric. As your shawl grows, this is a critical attribute to consider.