Conversion set for T4'20 to change it to your T4'21 Aluminum Solid version. Includes all necessary elements including aluminum solid framework, graphite top deck, human anatomy upstops & battery adj. width dishes, composite 4° c-hubs for human anatomy upstops, composite bumper upper holder brace, composite adj. battery power holders & backstops, springs, ECS drive shafts 52mm, aluminum steering plate 8mm, aluminum belt tensioner, aluminum motor mount, aluminum framework brace, aluminum rear suspension system, holders with centering pin, steel solid drive shafts along with other parts,