Populating list of custom class through inspector

HI!

I have a list of my abstract custom class "Stat" on my items in a game i'm making. I want to be able to populate this list through the inspector so that i can make multiple, different items easily. The problem is that i can't create instances of the "Stat" class through the inspector.

"Stat" class with sublasses:

 using UnityEngine;
 using System.Collections;
 
 [System.Serializable]
 abstract public class Stat : MonoBehaviour {
     public int value;
 
     public Stat (int value) {
         this.value = value;
     }
    
     abstract public string Print() ;
 }
 
 
 [System.Serializable]
 public class FireRateStat : Stat {
 
     public FireRateStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Fire rate: " + value + "/n";
     }
 }
 
 [System.Serializable]
 public class DamageStat : Stat {
     public DamageStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Damage: " + value + "/n";
     }
 }
 
 [System.Serializable]
 public class HealthStat : Stat {
 
     public HealthStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Health: " + value + "/n";
     }
 }
 
 [System.Serializable]
 public class HealthRegStat : Stat {
 
     public HealthRegStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Health regen: " + value + "/n";
     }
 }
 
 [System.Serializable]
 public class ShieldStat : Stat {
 
     public ShieldStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Shield: " + value + "\n";
     }
 }
 
 [System.Serializable]
 public class ShieldRegStat : Stat {
 
     public ShieldRegStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Shield Regen: " + value + "/n";
     }
 }
 
 [System.Serializable]
 public class MoveSpeedStat : Stat {
 
     public MoveSpeedStat(int value) : base(value) {
         this.value = value;
     }
 
     public override string Print() {
         return "Move Speed: " + value + "/n";
     }
 }

Item class:

 using System.Collections;
 using System.Collections.Generic;
 using System.Reflection;
 using UnityEngine;
 
 public enum Category
 {
     None,
     Engine,
     Shield,
     Weapon,
     Chassis,
 }
 
 public class ShipPart : MonoBehaviour {
 
     PlayerStats player;
 
     [TextArea]
     public string description;
     [TextArea]
     public string partName;
 
     public int buyValue;
     public int sellValue;
     public List<Stat> stats;
 
     [HideInInspector]
     public ItemImage itemImage;
     [HideInInspector]
     public string statsText = "";
 
     public Category category;
 
 
     public void UnassignSelf(bool removeItem = true) {
         if(itemImage != null)
         {
             itemImage.UnassignItem(removeItem);
         }
     }
 
     private void CreateStatsText () {
         foreach (Stat stat in stats) {
             statsText += stat.Print();
         }
     }
 
     public void UnapplyStats() {
         Debug.Log("Not implemented yet");
     }
 
     public List<Stat> GetStats() {
         return stats;
     }
 
     public void Start () {
 
         CreateStatsText();
     }
 }
 

Current inspector: