diff --git a/layouts/_default/single.html b/layouts/_default/single.html
index 89b61b2..efbeb39 100755
--- a/layouts/_default/single.html
+++ b/layouts/_default/single.html
@@ -4,7 +4,7 @@
 {{ end }}
 
 {{ define "main" }}
-  <article class="flex-l flex-wrap justify-between mw8 center ph3 ph0-l">
+  <article class="{{ $.Param "post_article_class"  | default "flex-l flex-wrap justify-between mw8 center ph3 ph0-l"}}">
 
     <header class="mt4 w-100">
       <p class="f6 b helvetica tracked">
@@ -14,7 +14,7 @@
           */}}
         {{with .CurrentSection.Title }}{{. | upper }}{{end}}
       </p>
-      <h1 class="f1 athelas mb1">
+      <h1 class="{{ $.Param "post_title_class"  | default "f1 athelas mb1" }}">
         {{- .Title -}}
       </h1>
       {{/* Hugo uses Go's date formatting is set by example. Here are two formats */}}
@@ -23,7 +23,7 @@
       </time>
     </header>
 
-    <main class="nested-copy-line-height lh-copy serif f4 nested-links nested-img mid-gray pr4-l w-two-thirds-l">
+    <main class="{{ $.Param "post_main_class"  | default "nested-copy-line-height lh-copy f4 nested-links nested-img mid-gray pr4-l w-two-thirds-l" }}">
         {{- .Content -}}
       {{- partial "tags.html" . -}}
       <div class="mt6">