diff --git a/eas/do_sims.sh b/eas/do_sims.sh
index b7566c3eba0b4a83475f8de5440ead1627dae70b..8a5e386f3ca9a6cff846181ac71d3ab6df0debd2 100755
--- a/eas/do_sims.sh
+++ b/eas/do_sims.sh
@@ -55,7 +55,8 @@ showhelp() {
   echo -e "  -w <working dir>                   : Working directory, where bin (run) files are located"
   echo -e "  -p <project name>                  : Project name (suggested format: NAMEXX)"
   echo -e "  -v <CORSIKA version>               : CORSIKA version"
-  echo -e "  -h <HE Int Model (EPOS|QGSII)>     : Define the high interaction model to be used"
+  echo -e "  -h <HE Int Model (EPOS|QGSII)>     : Define the high energy interaction model to be used. Default: QGSJET-II-04"
+  echo -e "  -f <LE Int Model (gheisha|fluka)>  : Define the lown energy interaction model to be used. Default: gheisha"
   echo -e "  -u <user name>                     : User Name."
   echo -e "  -j <procs>                         : Number of processors to use"
   echo -e
@@ -89,7 +90,7 @@ cta=false
 debug=false
 highsec=false
 sites=false
-usr="LAGO";
+usr="LAGO"
 vol=false
 alt=false
 altitude=0.
@@ -106,8 +107,9 @@ defaults=false
 ecut=800
 slurm=false
 
+
 echo
-while getopts 'w:k:p:t:v:u:h:s:j:c:b:m:n:r:i:o:q:a:?lydex' opt; do
+while getopts 'w:k:p:t:v:u:f:h:s:j:c:b:m:n:r:i:o:q:a:?lydex' opt; do
   case $opt in
     w)
       wdir=$OPTARG
@@ -138,6 +140,10 @@ while getopts 'w:k:p:t:v:u:h:s:j:c:b:m:n:r:i:o:q:a:?lydex' opt; do
       hig=$OPTARG
       echo -e "#  High Energy Interaction Model = $hig"
       ;;
+    f)
+      lemodel=$OPTARG
+      echo -e "#  Lew Energy Interaction Model = $lemodel"
+      ;;
     s)
       site=$OPTARG
       sites=true
@@ -252,6 +258,11 @@ if [ "X$hig" == "X" ]; then
   echo -e "#  INFO: High energy interaction model was not provided. Using default: $hig"
 fi
 
+if [ "X$lemodel" == "X" ]; then
+  lemodel="gheisha"
+  echo -e "#  INFO: Low energy interaction model was not provided. Using default: $lemodel"
+fi
+
 if [ "X$atm_model" == "X" ]; then
   atm_model="E1"
   echo -e "#  INFO: Atmospheric Model was not provided. Using default: $atm_model"
@@ -323,7 +334,7 @@ if $slurm; then
 	echo -e "#  INFO: SLURM mode is enable. Will not work in other environments."
 fi
 
-corsika_bin="corsika${ver}Linux_${hig}_gheisha"
+corsika_bin="corsika${ver}Linux_${hig}_${lemodel}"
 if [ ! -e $wdir/$corsika_bin ]; then
 	echo; echo -e "ERROR: Can't locate corsika executable file ($corsika_bin) in the working dir you provided. Please check."
     showhelp
@@ -421,7 +432,7 @@ if $slurm; then
 	rain="$rain -l"
 fi
 
-rain="$rain -r $wdir -v $ver -h $hig -b $prj/\$i-*.run"
+rain="$rain -r $wdir -v $ver -h $hig -f $lemodel -b $prj/\$i-*.run"
 # echo -e "#  INFO   : rain command: $rain"
 echo -e "#  INFO   : Calculations done. Now run the go_${prj}_* scripts in $wdir/"
 basenice=19
diff --git a/eas/rain.pl b/eas/rain.pl
index 2dddc388077e2a15eb68257f9d0ee590b2227517..c28279fdf317ab52005183df47a919edc033300f 100755
--- a/eas/rain.pl
+++ b/eas/rain.pl
@@ -89,6 +89,7 @@ my $grid = 0;
 my $imuaddi = 0;
 my $nofruns = 1;
 my $ecutshe = 800.;
+my $lemodel = "gheisha";
 
 sub get_answer {
   my $question = $_[0];
@@ -197,9 +198,13 @@ while ($_ = $ARGV[0]) {
     $heim = $ARGV[0];
     shift;
   }
+  if (/-f$/i) {
+    $lemodel = $ARGV[0];
+    shift;
+  }
 }
 
-my $package="corsika".$crk_ver."Linux_".$heim."_gheisha";
+my $package="corsika".$crk_ver."Linux_".$heim."_".$lemodel;
 $package = $package . "_thin" if ($ithin != 0);
 my $usage="
        $0 $VERSION\n
@@ -210,6 +215,7 @@ my $usage="
        -r  <working directory>             Specify where corsika bin files are located
        -v  <version>                       Corsika version number
        -h  <high energy interaction model> High energy interaction model used for compilation of CORSIKA (EPOS|QGSII|SIBYLL)
+       -f  <low energy interaction model>  Low energy interaction model used for compilation of CORSIKA (gheisha|fluka)
        -l                                  Enables SLURM cluster compatibility (with sbatch). 
        -t  <EFRCTHN> <WMAX> <RMAX>         Enables THIN Mode (see manual for pg 62 for values)
        -th <THINRAT> <WEITRAT>             If THIN Mode, select different thining levels for Hadronic (THINH) ...
@@ -438,6 +444,9 @@ for (my $i=0; $i < $nofruns; $i++) {
   }
   # LAGO ECUTS, minimum possible values as for the current corsika version
   my @ecuts=(0.05, 0.01, 0.00005, 0.00005);
+  if ($lemodel eq "fluka") {
+    $ecuts[0]=0.02;
+  }
   if ($highsec != 0) {
     @ecuts=($ecutshe, $ecutshe, $ecutshe, $ecutshe);
     $e_low = $ecutshe if ($e_low < $ecutshe);
@@ -616,4 +625,4 @@ unless ($grid != 0) {
   print "###################################################################\n";
   print "# BYE BYE\n";
   print "###################################################################\n";
-}
\ No newline at end of file
+}