diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableCollider.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableCollider.cs
index 9bacf616d..119b4712e 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableCollider.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/Blittables/BlittableCollider.cs
@@ -1,4 +1,5 @@
 using System;
+using Unity.Mathematics;
 using UnityEngine;
 
 namespace UniGLTF.SpringBoneJobs.Blittables
@@ -7,15 +8,35 @@ namespace UniGLTF.SpringBoneJobs.Blittables
     /// Blittableなコライダ
     /// </summary>
     [Serializable]
-    public struct BlittableCollider
+    public readonly struct BlittableCollider
     {
-        public BlittableColliderType colliderType;
-        public Vector3 offset;
-        public float radius;
-        // capsule tail or plane normal
-        public Vector3 tailOrNormal;
-        public int transformIndex;
+        private readonly float3x3 _data;
 
+        public BlittableColliderType colliderType => (BlittableColliderType)(int)_data.c2.y;
+        public float3 offset => _data.c0;
+        public float radius => _data.c2.x;
+        // capsule tail or plane normal
+        public float3 tailOrNormal => _data.c1;
+        public int transformIndex => (int)_data.c2.z;
+
+        public BlittableCollider(
+            float3 offset = default,
+            float radius = 0,
+            float3 tailOrNormal = default,
+            BlittableColliderType colliderType = default, 
+            int colliderTransformIndex = 0)
+        {
+            var c0 = offset;
+            var c1 = tailOrNormal;
+            var c2 = new float3(radius,(int)colliderType, colliderTransformIndex);
+            _data = new float3x3(c0, c1, c2);
+        }
+
+        public BlittableCollider SetTransformIndex(int index)
+        {
+            return new BlittableCollider(offset, radius, tailOrNormal, colliderType, index);
+        }
+        
         public void DrawGizmo(BlittableTransform t)
         {
             Gizmos.matrix = t.localToWorldMatrix;
diff --git a/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs b/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs
index f420ed10e..5822c248f 100644
--- a/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs
+++ b/Assets/UniGLTF/Runtime/SpringBoneJobs/InputPorts/FastSpringBoneBuffer.cs
@@ -86,8 +86,8 @@ namespace UniGLTF.SpringBoneJobs.InputPorts
                 blittableColliders.AddRange(spring.colliders.Select(collider =>
                 {
                     var blittable = collider.Collider;
-                    blittable.transformIndex = Array.IndexOf(Transforms, collider.Transform);
-                    return blittable;
+                    var transformIndex = Array.IndexOf(Transforms, collider.Transform);
+                    return blittable.SetTransformIndex(transformIndex);
                 }));
                 blittableJoints.AddRange(spring.joints
                     .Take(spring.joints.Length - 1).Select(joint =>
diff --git a/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs b/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs
index 58d6192b6..270658005 100644
--- a/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs
+++ b/Assets/VRM/Runtime/SpringBone/Jobs/FastSpringBoneReplacer.cs
@@ -40,13 +40,10 @@ namespace VRM.SpringBoneJobs
                             var c = new FastSpringBoneCollider
                             {
                                 Transform = group.transform,
-                                Collider = new BlittableCollider
-                                {
-                                    offset = collider.Offset,
-                                    radius = collider.Radius,
-                                    tailOrNormal = default,
-                                    colliderType = BlittableColliderType.Sphere
-                                }
+                                Collider = new BlittableCollider(
+                                    offset: collider.Offset,
+                                    radius: collider.Radius,
+                                    colliderType: BlittableColliderType.Sphere)
                             };
                             colliders.Add(c);
                         }
diff --git a/Assets/VRM10/Runtime/Components/Vrm10Runtime/FastSpringBoneBufferFactory.cs b/Assets/VRM10/Runtime/Components/Vrm10Runtime/FastSpringBoneBufferFactory.cs
index f176a5e19..ce1fa24c5 100644
--- a/Assets/VRM10/Runtime/Components/Vrm10Runtime/FastSpringBoneBufferFactory.cs
+++ b/Assets/VRM10/Runtime/Components/Vrm10Runtime/FastSpringBoneBufferFactory.cs
@@ -49,13 +49,11 @@ namespace UniVRM10
                    .Select(collider => new FastSpringBoneCollider
                    {
                        Transform = collider.transform,
-                       Collider = new BlittableCollider
-                       {
-                           offset = collider.Offset,
-                           radius = collider.Radius,
-                           tailOrNormal = collider.TailOrNormal,
-                           colliderType = TranslateColliderType(collider.ColliderType)
-                       }
+                       Collider = new BlittableCollider(
+                           offset: collider.Offset,
+                           radius: collider.Radius,
+                           tailOrNormal: collider.TailOrNormal,
+                           colliderType: TranslateColliderType(collider.ColliderType))
                    }).ToArray(),
                 joints = spring.Joints
                    .Select(joint => new FastSpringBoneJoint
diff --git a/Assets/VRM10_Samples/ClothSample/ClothWarp/Runtime/Jobs/ClothWarpJobRuntime.cs b/Assets/VRM10_Samples/ClothSample/ClothWarp/Runtime/Jobs/ClothWarpJobRuntime.cs
index e4461c273..8e2181786 100644
--- a/Assets/VRM10_Samples/ClothSample/ClothWarp/Runtime/Jobs/ClothWarpJobRuntime.cs
+++ b/Assets/VRM10_Samples/ClothSample/ClothWarp/Runtime/Jobs/ClothWarpJobRuntime.cs
@@ -193,14 +193,12 @@ namespace UniVRM10.ClothWarp.Jobs
                     var colliderTransformIndex = GetOrAddColliderTransform(collider.transform);
 
                     colliderRef.Add(colliderInfo.Count);
-                    colliderInfo.Add(new BlittableCollider
-                    {
-                        offset = collider.Offset,
-                        radius = collider.Radius,
-                        tailOrNormal = collider.TailOrNormal,
-                        colliderType = TranslateColliderType(collider.ColliderType),
-                        transformIndex = colliderTransformIndex,
-                    });
+                    colliderInfo.Add(new BlittableCollider(
+                                         offset: collider.Offset, 
+                                         radius: collider.Radius, 
+                                         tailOrNormal: collider.TailOrNormal, 
+                                         colliderType: TranslateColliderType(collider.ColliderType), 
+                                         colliderTransformIndex: colliderTransformIndex));
                     _colliders.Add(collider);
                 }