On list is two pieces of heatsink U-shape mounting blocks that is specifically to be used with TO-3 transistors. By mounting TO-3 transistors onto this mounting plate, TO-3 transistors can be then mounted onto the main big heatsinks, such as standard rectangular block finned heatsink for effective heat dissipation, while the TO-3 transistors can be directly soldered on the PCB. This greatly enhances performance of transistors that has high input capacitance such as MOSFETs. Applications of this block can be seen in the pictures below. The block is to be mounted on the actual heatsink with 4 pieces of M4 screws. This listing for two pieces of U-shape mounting blocks. NO PCB is including in this listing. The plate with the assembled PCB in the pictures is for application reference. Dimension : TO-3 plate dimension : 120mm(l) x 48mm(w) x 14mm(h1) x 4mm(h2) where h1 is the height on two sides to be mounted on the heatsink, and h2 is the plate thickness for mounting the TO-3 transistor(s). Air shipping cost worldwide by registered airmail is US$12.00. We welcome combined shipping.