The size is laser imprinted on each tip. SPIN tips can be used with TWIST red cables.
Most TWIST & SPIN parts and pieces are coded [S] for the small diameter screw size and [L] for the large diameter screw size. Within the TWIST & SPIN systems:
Parts coded [S] are compatible with other [S] coded parts and tip sizes US2 (2.75 mm) through US8 (5 mm).
Parts coded [L] are compatible with other [L] coded parts and tip sizes US9 (5.5 mm) through US15 (10 mm).