Surface Shaders have Slight Trasparency. Why?

I'm trying to make a simple surface shader that will allow for the use of a transparency map. It seems to be fine until a view the "donut" type sample on the bottom left of the Unity UI. I can see a slight transparency to it, even when there's no map added, an all white map is used or I just set o.Alpha to 1;

My code:

 Shader "James Kyle/Surface Shaders/007 - Colour Ramp Transparency Normal Rim Lighting" 
 {
     Properties 
     {
         _ColorTint ("Texture Tint", Color) = (1,1,1,1)
         _MainTex ("Texture", 2D) = "white" {}
         _AlphaTex ("Alpha Map", 2D) = "white" {}
         _Ramp ("Shader Ramp", 2D) = "gray" {}
         _BumpTex ("Normal Map", 2D) = "bump" {}
         _RimColor ("Rim Colour", Color) = (1,1,1,1)
         _RimPower ("Rim Power", Range(0.5, 8.0)) = 3.0
     }
     
     SubShader 
     {
         Tags 
         {
             "Queue"="Transparent"
             "RenderType"="Opaque" 
         }
         
         CGPROGRAM
         #pragma surface surf Ramp alpha
         
         
         struct Input {
             float2 uv_MainTex;
             float2 uv_AlphaTex;
             float2 uv_BumpTex;
             float3 viewDir;
         };
         
         float4 _ColorTint;
         sampler2D _MainTex;
         sampler2D _AlphaTex;
         sampler2D _Ramp;
         sampler2D _BumpTex;
         float4 _RimColor;
         float _RimPower;        
 
         // Custom lighting model...
         half4 LightingRamp (SurfaceOutput s, half3 lightDir, half atten) 
         {
             half NdotL = dot (s.Normal, lightDir);
             half diff = NdotL * 0.5 + 0.5;
             half3 ramp = tex2D (_Ramp, float2(diff,diff)).rgb;
             half4 c;
             
             c.rgb = s.Albedo * _LightColor0.rgb * ramp * (atten * 2);
             c.a = s.Alpha;
             return c;
         }
       
         
                 
         void surf (Input IN, inout SurfaceOutput o) 
         {
             o.Albedo     = tex2D(_MainTex, IN.uv_MainTex).rgb * _ColorTint.rgb;
             o.Alpha        = tex2D(_AlphaTex, IN.uv_AlphaTex).a;
             o.Normal    = UnpackNormal(tex2D(_BumpTex, IN.uv_BumpTex));
             half rim = 1 - saturate(dot(normalize(IN.viewDir), o.Normal));
             o.Emission     = _RimColor.rgb * pow(rim, _RimPower);
         }
         
         ENDCG
     } 
     FallBack "Diffuse"
 }

Digging around the only thing I can find that seems similar is this, but I've added the "Queue" = "Transparent" tag to no improvement. Can anyone see any reason why this is working like this? I'm at a total loss.