 Series 5 and Series 4 (Mini) machines have a freewheel mounted in the conventional position on the rear wheel (In Series 3 the freewheel, a commonly available Shimano 18t model, is part of the metal and plastic bottom bracket/crankset assembly) and a metal bottom bracket shell which incorporates an eccentric housing to adjust belt tension.Alternative folding handlebars which give more knee clearance for the taller rider are available for the Series 5; these may be retro-fitted in place of the standard folding handlebars on Series 3 and Series 4 (Mini).A number of unlicensed copies of Strida are manufactured in several countries (China, Thailand), and are sold with names such as "Folding bike Strida" or STRDA.