# Combining boundaries

Hello,

I am trying to group some surfaces together into a boundary condition, and currently, each surface gets the name I want, but they are not in the same boundary condition. I guess what happens is, each boundary index is assigned the corresponding boundary name, but they remain separate boundaries.

My code is as follows:

``````from netgen.csg import *

cube = OrthoBrick ( Pnt(-0.5, -0.5, -0.3), Pnt(0.5, 0.5, 0.3) ) #Scaled up 1000 times
holeX = Cylinder ( Pnt(-0.5, 0, 0), Pnt(0.5, 0, 0), 0.2)
holeY1 = Cylinder ( Pnt(0, -5, 0.3), Pnt(0, 5, 0.3), 0.2)
holeY2 = Cylinder ( Pnt(0, -5, -0.3), Pnt(0, 5, -0.3), 0.2)
cut1 = cube - holeX
cut2 = cut1 - holeY1
cut3 = cut2 - holeY2
pX = Plane(Pnt(0.5,0,0),Vec(1,0,0))
nX = Plane(Pnt(-0.5,0,0),Vec(-1,0,0))
pY = Plane(Pnt(0,0.5,0),Vec(0,1,0))
nY = Plane(Pnt(0,-0.5,0),Vec(0,-1,0))
pZ = Plane(Pnt(0,0,0.3),Vec(0,0,1))
nZ = Plane(Pnt(0,0,-0.3),Vec(0,0,-1))
boundingBox = pX*nX*pY*nY*pZ*nZ
Budapest = cut3*boundingBox
Budapest.bc('FSI')

# Mesh for bounding box
bbgeo=CSGeometry()
bbngmesh = bbgeo.GenerateMesh(maxh=0.1)
bbmesh = Mesh(bbngmesh)

geo=CSGeometry()

from ngsolve.comp import Mesh
netgenMesh=geo.GenerateMesh(maxh=0.025)
mesh = Mesh(netgenMesh)
# Marking periodic surfaces
geo.PeriodicSurfaces(pX,nX)
geo.PeriodicSurfaces(pY,nY)
geo.PeriodicSurfaces(pZ,nZ)

print(mesh.GetBoundaries())``````

And this prints:

How can I combine or group together boundaries, so that in the above case, there is only one boundary called ‘FSI’?