Shader Transparency problem

Hello, i have a shader to edit color and alpha by vertices, but i cant see the inside triangles color properly from the outside. Whats happening? How can i fix it?
I think it isnt a problem of the transparency part, because if i put a cube inside i can see it well.

You can see the colored part well from the inside, but not from the outside:

Shader "Custom/PruebaTransparente" {
Properties{
	_Color("Color", Color) = (1,1,1,0.5)
	_MainTex("Albedo (RGB)", 2D) = "white" {}
_Glossiness("Smoothness", Range(0,1)) = 0.5
	_Metallic("Metallic", Range(0,1)) = 0.0
}
SubShader{
	Tags{ "Queue" = "Transparent" "IgnoreProjector" = "True"  "RenderType" = "Transparent" }
	Blend SrcAlpha OneMinusSrcAlpha
	
	LOD 200
	Pass{
		Cull Off
	}
	CGPROGRAM
		#pragma surface surf Standard vertex:vert fullforwardshadows lambert alpha:fade
		
		//
		#pragma target 3.0
		struct Input {
			float2 uv_MainTex;
			float3 vertexColor; // Vertex color stored here by vert() method
		};

		struct v2f {
			float4 pos : SV_POSITION;
			fixed4 color : COLOR;
		};

		void vert(inout appdata_full v, out Input o)
		{
			UNITY_INITIALIZE_OUTPUT(Input,o);
			o.vertexColor = v.color; // Save the Vertex Color in the Input for the surf() method
		}

		sampler2D _MainTex;

		half _Glossiness;
		half _Metallic;
		fixed4 _Color;

		void surf(Input IN, inout SurfaceOutputStandard o)
		{
			// Albedo comes from a texture tinted by color
			fixed4 c = tex2D(_MainTex, IN.uv_MainTex) * _Color;
			o.Albedo = c.rgb * IN.vertexColor; // Combine normal color with the vertex color
												// Metallic and smoothness come from slider variables
			o.Metallic = _Metallic;
			o.Smoothness = _Glossiness;
			o.Alpha = c.a;
		}
	ENDCG
}
FallBack "Diffuse"

}

I change my shader to the next one, and its doing the same thing

Shader "Custom/PruebaTransparente" {
	Properties{
		_Color("Color", Color) = (1,1,1,1)

	}
	SubShader{
		Tags{ "Queue" = "Transparent"  "RenderType" = "Opaque" }
		Blend SrcAlpha OneMinusSrcAlpha
		
		LOD 200
		
		
		Pass{
		ZWrite On
		Cull Off
		}
		
	}

}

I fixed it with “AlphaTest comparison AlphaValue”
link text

Pass{
		Cull Off
		AlphaTest Greater 0.5
}