Billboarding

Im having trouble with bill boarding something with a basic script ( Shown below ). Now im comparing this to the grass Billboarding built into unity terrain system. My Billboarding is slightly rotated so it looks weird, now how can i make my Billboarding like the grass system?

 using UnityEngine;
 using System.Collections;
 
 public class CameraFacing : MonoBehaviour
 { 
     public Camera cameraToLookAt;
         
      void Update()
      {
          Vector3 v = cameraToLookAt.transform.position - transform.position;
          v.x = v.z = 0.0f;
          
              v.y = 90;
          transform.LookAt(cameraToLookAt.transform.position - v);
          }
 
 }