The Alligt chain idlers now come in a range of sizes both with and without teeth. Teeth are required on the drive side of an idler, where the chain is under tension. Teeth are optional where the chain is slack, on the return side of the chainrun.
The chainrings are made of PA6 plastic with 30% glassfibre for strength. The bearings have an 8 mm hole, this being the size of fixing used on many recumbents, including the Alleweder, Mango and Quest velomobiles.
Two sets of 608 bearings are fitted to each idler with a central hole for an 8 mm axle. Some of the 100 mm diameter idlers are also available with larger bearings which have 10 mm central holes. Note that the smaller sizes cannot be fitted with bearings for 10 mm axles.
Toothed idlers can be delivered with either hard plastic, aluminium or steel teeth with a progressively longer expected lifetime. SKF bearings are an option for the steel teeth idlers as their longer life-span makes sense only when combined with the longer lasting teeth.