The original sea doo wear rings were made of a polyethylene plastic and fiberglass sandwiched together. Starting in 2002 with the first four stroke jet ski made by seadoo, the 4 tech, seadoo changed to one piece Delrin construction. The Watercraft Superstore sells SBT Delrin wear rings. The SBT wear rings for all makes and models of Seadoo uses the Delrin one piece construction technology. So in effect, SBT took the latest technology and applied it to all of the wear rings even the earlier model ones that were the plastic/fiberglass construction.
One piece Delrin construction has its advantages. Delrin, is an engineering plastic, a polymer with the chemical formula -(-O-CH2-)n-. It is often marketed and used as a metal substitute. Delrin is a lightweight, low-friction, and wear-resistant thermoplastic with good physical and processing properties and capable of operating in temperatures in excess of 90 degrees Celsius (approximately 200 degrees Fahrenheit). Typical applications for injection-molded POM include high performance engineering components (e.g. gear wheels, ski bindings, fasteners, lock systems, wear rings) and the material is widely used in the automotive and consumer electronics industry. There are special grades that offer higher mechanical toughness, stiffness or low friction/ wear properties. Delrin is perfect for seadoo wear ring because it has good hardness and tensile strength. It is also forgiving as the sea doo wear rings can get little nicks and cuts without sacrificing overall performance.
As a side note of interest, Delrin was used by Mattel from 1968 to 1972 to produce the low-friction wheel bearings found on redline Hot Wheels. It is also used in yo-yos such as the Silk by Alchemy yoyos, Lyn Fury by YoYoJam, and the Milk by Born Crucial. Delrin's lubricity (when machined on a lathe) yields a yo-yo with significantly less friction.