Pro-Series 3/16″ SK16 Lyndex Style Collet ~ Collapse range is 0.168-0.188″. ~ Vacuum quenching heat treatment to hardness HRC46~50. ~ Runout is less than or equal to 5 Micron. ~ Collet front cone convex platform design reduces the entry of dust and chips increasing service life. ~ The SK slim collet system features an 8° taper angle versus the 16° taper for ER type collets. ~ The SK style collet has greater gripping force than ER collets. ~ SK collets sit deeper in the tool holder compared to TG and ER type collet systems resulting in higher accuracy and rigidity.