diff --git a/MetaballsKit/Metaballs.swift b/MetaballsKit/Metaballs.swift
index 2f81f52..1af6d9d 100644
--- a/MetaballsKit/Metaballs.swift
+++ b/MetaballsKit/Metaballs.swift
@@ -36,7 +36,7 @@ public struct Field {
         return CGRect(origin: CGPoint(), size: size)
     }
 
-    init(size s: CGSize) {
+    public init(size s: CGSize) {
         size = s
     }