diff --git a/src/rect.rs b/src/rect.rs
index 2487df8..f30fad8 100644
--- a/src/rect.rs
+++ b/src/rect.rs
@@ -1,17 +1,17 @@
-use num::Num;
 use crate::vec2::Vec2;
+use num::{Num, ToPrimitive};
 
 #[derive(Copy, Clone)]
-pub struct Rect<T: Num + Copy> {
+pub struct Rect<T: Num + Copy + ToPrimitive> {
     pub pos: Vec2<T>,
     pub size: Vec2<T>,
 }
 
-impl<T: Num + Copy> Rect<T> {
+impl<T: Num + Copy + ToPrimitive> Rect<T> {
     pub fn new(x: T, y: T, w: T, h: T) -> Rect<T> {
         Rect {
-            pos: Vec2{x, y},
-            size: Vec2{x: w, y: h},
+            pos: Vec2 { x, y },
+            size: Vec2 { x: w, y: h },
         }
     }
 }
diff --git a/src/vec2.rs b/src/vec2.rs
index 0cf1959..fb0740d 100644
--- a/src/vec2.rs
+++ b/src/vec2.rs
@@ -6,7 +6,7 @@ pub struct Vec2<T: Num + Copy + ToPrimitive> {
     pub y: T,
 }
 
-impl<T: Num + Copy> Vec2<T> {
+impl<T: Num + Copy + ToPrimitive> Vec2<T> {
     //pub static
     pub fn zero() -> Self {
         Vec2 {
@@ -17,11 +17,11 @@ impl<T: Num + Copy> Vec2<T> {
 
     //pub
     pub fn size(&self) -> usize {
-        (self.x * self.y) as usize
+        (self.x * self.y).to_usize().unwrap()
     }
 }
 
-impl<T: Num + Copy + Default> Default for Vec2<T> {
+impl<T: Num + Copy + ToPrimitive + Default> Default for Vec2<T> {
     fn default() -> Self {
         Vec2 {
             x: T::default(),