hollow is part of:

hollow contains:

Full expansion for hollow:
   100%  11L Hollow Flex-System Tube
   100%  12L Hollow Flex-System Tube
   100%  13L Hollow Flex-System Tube
   100%  14L Flexible Ribbed Tube
   100%  14L Hollow Flex-System Tube
   100%  15L Hollow Flex-System Tube
   100%  19L Hollow Flex-System Tube
   100%  21L Hollow Flex-System Tube
   100%  24L Hollow Flex-System Tube
   100%  3x3x2 Treaded Hollow Space Wheel
   100%  45L Hollow Flex-System Tube
   100%  4x4x2 Hollow Cone Brick
   100%  4x4x3 Treaded Hollow Space Wheel
   100%  9L Flexible Ribbed Tube