John Guest speed fit connection for water filter and water coolers are stocked by Aqua One Australia. Genuine John Guest UK Premium Fittings Available in Metric and Imperial – 1/4″, 5/16″, 3/8″, 1/2″, 3/4 “, 4mm, 6mm, 8mm, 10mm, 12mm and more. What ever your job John Guest will make any job and easy job.