This is a 30mm aluminum extension adapter. It is lightweight and durable. It is compatible with a 5mm base diameter. The dimensions are: 30mm for the wider pipe, 30mm for the narrower pipe, 10mm overlap, 50mm total length, and approximately 1.2g in weight. Since it is handmade, there may be slight variations. ★ Even with the same 5mm base diameter, there may be slight differences in thickness depending on the manufacturer. If adjustment is needed, please use aluminum foil, etc. (The holes are made slightly wider and the shaft slightly narrower for easier adjustment.) ◆ If you purchase multiple sets, we will reduce the shipping cost, so please comment in advance.