diff --git a/iroh-relay/src/relay_map.rs b/iroh-relay/src/relay_map.rs
index 355c3dc8f2..3a01f99e64 100644
--- a/iroh-relay/src/relay_map.rs
+++ b/iroh-relay/src/relay_map.rs
@@ -112,11 +112,34 @@ impl RelayMap {
         self.relays.write().expect("poisoned").remove(url)
     }
 
+    /// Joins this `RelayMap` with another one into a new one
+    pub fn join(self, other: RelayMap) -> RelayMap {
+        {
+            let mut a = self.relays.write().expect("poisoned");
+            let b = other.relays.read().expect("poisoned");
+            a.extend(b.iter().map(|(a, b)| (a.clone(), b.clone())));
+        }
+        self
+    }
+}
+
+impl Extend<(RelayUrl, Arc<RelayConfig>)> for RelayMap {
     /// Extends this `RelayMap` with another one.
-    pub fn extend(&self, other: &RelayMap) {
+    ///
+    /// You can use this like this:
+    ///
+    /// ```rust
+    /// # let relay_map_a: RelayMap = { unimplemented!() };
+    /// # let relay_map_b: RelayMap = { unimplemented!() };
+    ///
+    /// relay_map_a.extend(relay_map_b.relays::<Vec<_>>());
+    /// ```
+    fn extend<I>(&mut self, iter: I)
+    where
+        I: IntoIterator<Item = (RelayUrl, Arc<RelayConfig>)>,
+    {
         let mut a = self.relays.write().expect("poisoned");
-        let b = other.relays.read().expect("poisoned");
-        a.extend(b.iter().map(|(a, b)| (a.clone(), b.clone())));
+        a.extend(iter);
     }
 }