diff --git a/activitystreams-types/src/object/properties.rs b/activitystreams-types/src/object/properties.rs
index 9154bd6..8ba8465 100644
--- a/activitystreams-types/src/object/properties.rs
+++ b/activitystreams-types/src/object/properties.rs
@@ -578,13 +578,12 @@ properties! {
                 "",
                 "If not specified, the default is assumed to be \"m\" for meters.",
                 "",
-                "TODO: encode rage as any of `\"cm\"` | `\"feet\"` | `\"inches\"` | `\"km\"` | `\"m\"` | `xsd:anyUri`",
-                "- Range: `xsd:anyUri` | `xsd:string`",
+                "- Range: `\"cm\"` | `\"feet\"` | `\"inches\"` | `\"km\"` | `\"m\"` | `xsd:anyUri` | `xsd:anyUri`",
                 "- Functional: true",
             ],
             types [
+                Length,
                 XsdAnyUri,
-                XsdString,
             ],
             functional,
         },
diff --git a/activitystreams-types/src/primitives/length.rs b/activitystreams-types/src/primitives/length.rs
new file mode 100644
index 0000000..8530792
--- /dev/null
+++ b/activitystreams-types/src/primitives/length.rs
@@ -0,0 +1,118 @@
+#[derive(
+    Clone, Debug, Eq, Hash, Ord, PartialEq, PartialOrd, serde::Deserialize, serde::Serialize,
+)]
+#[serde(untagged)]
+pub enum Length {
+    #[serde(rename = "cm")]
+    Centimeters,
+
+    #[serde(rename = "feet")]
+    Feet,
+
+    #[serde(rename = "inches")]
+    Inches,
+
+    #[serde(rename = "km")]
+    Kilometers,
+
+    #[serde(rename = "m")]
+    Meters,
+}
+
+#[derive(Clone, Debug, thiserror::Error)]
+#[error("Could not parse units")]
+pub struct LengthError;
+
+impl Length {
+    pub fn is_centimeters(&self) -> bool {
+        match self {
+            Length::Centimeters => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_feet(&self) -> bool {
+        match self {
+            Length::Feet => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_inches(&self) -> bool {
+        match self {
+            Length::Inches => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_kilometers(&self) -> bool {
+        match self {
+            Length::Kilometers => true,
+            _ => false,
+        }
+    }
+
+    pub fn is_meters(&self) -> bool {
+        match self {
+            Length::Meters => true,
+            _ => false,
+        }
+    }
+}
+
+impl Default for Length {
+    fn default() -> Self {
+        Length::Meters
+    }
+}
+
+impl std::str::FromStr for Length {
+    type Err = LengthError;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "cm" => Ok(Length::Centimeters),
+            "feet" => Ok(Length::Feet),
+            "inches" => Ok(Length::Inches),
+            "km" => Ok(Length::Kilometers),
+            "m" => Ok(Length::Meters),
+            _ => Err(LengthError),
+        }
+    }
+}
+
+impl std::convert::TryFrom<&str> for Length {
+    type Error = LengthError;
+
+    fn try_from(s: &str) -> Result<Self, Self::Error> {
+        s.parse()
+    }
+}
+
+impl std::convert::TryFrom<&mut str> for Length {
+    type Error = LengthError;
+
+    fn try_from(s: &mut str) -> Result<Self, Self::Error> {
+        s.parse()
+    }
+}
+
+impl std::convert::TryFrom<String> for Length {
+    type Error = LengthError;
+
+    fn try_from(s: String) -> Result<Self, Self::Error> {
+        s.parse()
+    }
+}
+
+impl std::fmt::Display for Length {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            Length::Centimeters => write!(f, "cm"),
+            Length::Feet => write!(f, "feet"),
+            Length::Inches => write!(f, "inches"),
+            Length::Kilometers => write!(f, "km"),
+            Length::Meters => write!(f, "meters"),
+        }
+    }
+}
diff --git a/activitystreams-types/src/primitives/mod.rs b/activitystreams-types/src/primitives/mod.rs
index 996e913..f504281 100644
--- a/activitystreams-types/src/primitives/mod.rs
+++ b/activitystreams-types/src/primitives/mod.rs
@@ -1,3 +1,4 @@
+mod length;
 mod mime_media_type;
 mod rdf_lang_string;
 mod xsd_any_uri;
@@ -9,6 +10,7 @@ mod xsd_non_negative_integer;
 mod xsd_string;
 
 pub use self::{
+    length::Length,
     mime_media_type::{MimeMediaType, MimeMediaTypeError},
     rdf_lang_string::RdfLangString,
     xsd_any_uri::{XsdAnyUri, XsdAnyUriError},
diff --git a/activitystreams-types/src/primitives/xsd_string.rs b/activitystreams-types/src/primitives/xsd_string.rs
index 5db7d6b..16cc16a 100644
--- a/activitystreams-types/src/primitives/xsd_string.rs
+++ b/activitystreams-types/src/primitives/xsd_string.rs
@@ -26,6 +26,30 @@ impl From<XsdString> for String {
     }
 }
 
+impl AsRef<str> for XsdString {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
+
+impl AsRef<String> for XsdString {
+    fn as_ref(&self) -> &String {
+        &self.0
+    }
+}
+
+impl AsMut<str> for XsdString {
+    fn as_mut(&mut self) -> &mut str {
+        &mut self.0
+    }
+}
+
+impl AsMut<String> for XsdString {
+    fn as_mut(&mut self) -> &mut String {
+        &mut self.0
+    }
+}
+
 impl std::fmt::Display for XsdString {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         std::fmt::Display::fmt(&self.0, f)