For scratch building and custom work it’s worth noting that each tube fits inside the other the 3mm 0.225mm wall tube fits inside this tube and the 4mm 0.225mm wall tube fits over this tube
The 0.225mm wall tube is part of the telescopic brass tube range where the following applies
2mm 0.225mm wall slides into 2.5mm 0.225mm wall
2.5mm 0.225mm wall slides into 3mm 0.225mm wall
3mm 0.225mm wall slides into 3.5mm 0.225mm wall
3.5mm 0.225mm wall slides into 4mm 0.225mm wall
4mm 0.225mm wall slides into 4.5mm 0.225mm wall
4.5mm 0.225mm wall slides into 5mm 0.225mm wall
. More brass tube available click here