4mm, gauge 6-8 red plastic sprues for larger castings and acid-etch bridges. These sprues are specially designed to provide consistant high quality in conventional or ringless casting. The hollow interior allows for rapid elimination of wax and gases to prevent cracking, carbonisation and vapour pressure damage. There is no need to coat with wax and the reservoir prevent porosity and provides an anchor site for auxiliary sprues. The high-quality rigid plastic provides maximum support plus extra-clean burnout and the tapered sprue tip creates a 'nozzle-effect' for better flow of alloy.