# About User Defined Weight window

Dear FLUKA Experts,

In MCNP, we can use the card “MESH” to define a set of weight windows covering the regions of interest. The “MESH” card is similar to the “usrbin” card in FLUKA, but is used to generate the weight windows for a set of regions. Then we can use this generated weight windows input file for further simulations without defining the weighting windows region by region.
Does FLUKA also have this kind of function? I hope to get your answer. Thanks a lot!

no FLUKA do not have this feature with cards, however you can perform something similar (importance biasing overlaid on the geometry but not weight windows) using the routine 13.2.24. usimbs.f — FLUKA Manual

Look also the lecture of the advanced course on biasing on how to use it

thanks a lot. It’s really helpful for me.