diff --git a/defaults/settings.json b/defaults/settings.json
index e230bda..db21d2b 100644
--- a/defaults/settings.json
+++ b/defaults/settings.json
@@ -1,4 +1,5 @@
 {
+    "filename": "smart-grid",
     "outputStyle": "less",
     "columns": 12,
     "offset": "30px",
diff --git a/index.js b/index.js
index a340024..e57dac7 100644
--- a/index.js
+++ b/index.js
@@ -30,7 +30,7 @@ module.exports = function(dest, options){
             console.log('It`s test mode, because you don`t set destination folder');
         }
         else{
-            var buildFile = dest + '/smart-grid.' + res.type;
+            var buildFile = dest + '/' + options.filename + '.' + res.type;
             fs.writeFileSync(buildFile, res.grid);
             console.log('Grid placed into ' + buildFile);
         }
diff --git a/system/helpers.js b/system/helpers.js
index e230ed9..1173462 100644
--- a/system/helpers.js
+++ b/system/helpers.js
@@ -29,8 +29,12 @@ Helpers.prototype.parseUnit = function(str){
         res.value = str.substr(0, str.length - 1);
         res.unit = '%';
     }
+    else if(this.isRem(str)){
+        res.value = str.substr(0, str.length - 3);
+        res.unit = 'rem';
+    }
     else{
-        throw new Error('what is "' + str + '" value? We use px and %.');
+        throw new Error('what is "' + str + '" value? We use px, % and rem.');
     }
     
     return res;
@@ -44,6 +48,10 @@ Helpers.prototype.isPercentage = function(str){
     return str.substr(-1) === '%';
 }
 
+Helpers.prototype.isRem = function(str){
+    return str.substr(-3) === 'rem';
+}
+
 Helpers.prototype.math = function(a, b, op){
     var res = null;