3D-printed. This is a part for attaching KATO couplers (close-coupling type) to TOMIX, Greenmax, Micro Ace, etc., models. TN couplers are expensive! You want realistic coupling faces and spacing! This product is recommended for those people. When using, you may need to cut a part of the product, as with the installation of TN couplers. This product includes 20 pieces. Other quantities are available in other listings, or please feel free to inquire in the question section, and we will list them. Separately, KATO product 11-731 is required, and assembly is necessary. Depending on the track environment (sharp curves, layouts with gradients, etc.), you may need to use 11-730. We also sell pre-assembled products with all couplers attached, so if you find the processing troublesome or are not good at it, please purchase those. Additional quantities and bulk purchases are available at a great price. Please feel free to contact us.