arch is part of:

arch contains:
    50%  half-arch

Full expansion for arch:
   100%  1x12x3 Staired Full-Arch Brick
   100%  1x12x5 Smooth-Round Full-Arch Brick
   100%  1x2x2.5 Arch Window Frame
   100%  1x2x2.5 Arch Window Mullion, Barbs
   100%  1x2x2.5 Arch Window Mullion, Lattice
   100%  1x3x1 Full-Arch Brick
   100%  1x4x1 Full-Arch Brick
   100%  1x4x2 Full-Arch Brick
   100%  1x6x1 Full-Arch Brick
   100%  1x6x2 Full-Arch Brick
   100%  1x8x2 Full-Arch Brick
   100%  2x8x3 Full-Arch Brick
    70%  2x8x2 Trapezoid. Arch Brick, ToolDeco
    70%  2x8x2 Trapezoidal Arch Brick
    50%  1x3x2 Smooth-Round Half-Arch Brick
    50%  1x5x4 Staired Half-Arch Brick
    50%  1x6x2 Smooth-Round Full-Arch Brick
    50%  1x6x3 Smooth-Round Half-Arch Brick
    50%  3x4x6 Curved-Top Side Thin-Wall
    40%  1x4x4 Staired Half-Inverse-Arch Brick
    40%  2x3x2 DUPLO Inverse-Half-Arch Brick
    40%  2x6x2 DUPLO Dual-Inv-Half-Arch Brick
    20%  3x3x6 Curved-Top Corner Thin-Wall
    15%  1x1x1.3 Half-Round-Top Brick w/Plate
     5%  1x4x1.3 Half-Round-Top Brick w/Plate