We have a variety of building block upgrade options: Over 600 Bricks set available in our store More than 50 power upgrade kits available in our store More than 20 kinds of spare parts sets, you can do STEM, EV3, MOC and other DIY, you can find tread,sprocket,wheel,large,link,chain,holes,and,reinforced,rim,tire,wedge,belt,pulley,bush ,axle,connector,perpendicular,pins,bent,friction,ridges,notched,pneumatic,liftarm,modified,frame,thick,gear,tooth,knob,cog,double,bevel,rack,and other spare parts, Finest quality meaterials, affordable and durable.