diff --git a/Chickensoft.Collections.Tests/src/extensions/HashSetExTest.cs b/Chickensoft.Collections.Tests/src/extensions/HashSetExTest.cs
new file mode 100644
index 0000000..d4deb16
--- /dev/null
+++ b/Chickensoft.Collections.Tests/src/extensions/HashSetExTest.cs
@@ -0,0 +1,25 @@
+namespace Chickensoft.Collections.Tests;
+
+using System.Collections.Generic;
+using Shouldly;
+using Xunit;
+
+public class HashSetExTest {
+  [Fact]
+  public void WithIncludesItem() {
+    var set = new HashSet<int> { 1, 2, 3 };
+    var result = set.With(4);
+
+    result.ShouldContain(4);
+    result.Count.ShouldBe(4);
+  }
+
+  [Fact]
+  public void WithoutExcludesItem() {
+    var set = new HashSet<int> { 1, 2, 3 };
+    var result = set.Without(2);
+
+    result.ShouldNotContain(2);
+    result.Count.ShouldBe(2);
+  }
+}
diff --git a/Chickensoft.Collections/src/extensions/HashSetEx.cs b/Chickensoft.Collections/src/extensions/HashSetEx.cs
new file mode 100644
index 0000000..b567629
--- /dev/null
+++ b/Chickensoft.Collections/src/extensions/HashSetEx.cs
@@ -0,0 +1,33 @@
+namespace Chickensoft.Collections;
+
+using System.Collections.Generic;
+
+/// <summary>
+/// <see cref="HashSet{T}" /> extensions.
+/// </summary>
+public static class HashSetEx {
+  /// <summary>
+  /// Creates a copy of the hash set with the specified item included.
+  /// </summary>
+  /// <typeparam name="T">Type of the item.</typeparam>
+  /// <param name="set">Hash set.</param>
+  /// <param name="item">Item to include.</param>
+  /// <returns>A new hash set.</returns>
+  public static HashSet<T> With<T>(this HashSet<T> set, T item) {
+    var copy = new HashSet<T>(set) { item };
+    return copy;
+  }
+
+  /// <summary>
+  /// Creates a copy of the hash set with the specified item excluded.
+  /// </summary>
+  /// <typeparam name="T">Type of the item.</typeparam>
+  /// <param name="set">Hash set.</param>
+  /// <param name="item">Item to exclude.</param>
+  /// <returns>A new hash set.</returns>
+  public static HashSet<T> Without<T>(this HashSet<T> set, T item) {
+    var copy = new HashSet<T>(set);
+    copy.Remove(item);
+    return copy;
+  }
+}
diff --git a/global.json b/global.json
index 4c868ba..510f4d9 100644
--- a/global.json
+++ b/global.json
@@ -4,6 +4,6 @@
   },
   "sdk": {
     "rollForward": "major",
-    "version": "9.0.100-rc.1.24452.12"
+    "version": "8.0.401"
   }
 }
diff --git a/renovate.json b/renovate.json
index 8ea4779..bf94541 100644
--- a/renovate.json
+++ b/renovate.json
@@ -13,7 +13,8 @@
       ],
       "groupName": "all dependencies",
       "groupSlug": "all-deps",
-      "automerge": true
+      "automerge": true,
+      "allowedVersions": "!/preview/"
     },
     {
       "matchPackagePrefixes": [