ShrinKit 321 Basic Heat-shrink Tubing Kit The ShrinKit 321 Basic contains a selection of black heat-shrink tubing in a range of 5 sizes and has an application range from 1 mm to 16 mm. Features and Benefits • Dielectric strength: 20 kV/mm according to ASTM D 2671 • Tubing supplied in a useful and compact kit • Kit contains 220 precut pieces in five different sizes • Ideal ratio of 3:1 • Self extinguishing tubing