I assume that you mean
http://www.bricklink.com/catalogItem.asp?P=15301c01 if you talk about 15400?
It seems that bricklink has the wrong number for the complete assembly because TLG calles it also 15400 (
http://brickset.com/parts/design-15400)
Edit:
according to LDD 15301c01 can not be the correct number because 15301 has nothing to do with this part.
Sadly LDD has no shape for the number 15400. But 15303 is present in LDD. So maybe someone can make a quick mockup for you.
Mmhhh... 15400 is available in LDD! I guess that 15301 is design number of the lower part, maybe 15302 is upper part (but it could be the spring too) and 15400 is the design number for assembly (
http://brickset.com/parts/design-15400). Could someone be kind enough to open a part and verify this hypothesis?
Many thanks to all for your very quick response!
I somehow missed part 15100. Sorry!
I just updated the L3b-File with part 15100.