create a class called class1.cs
inside your public partial on both form1 and form 2 add the following
class1 myclass = new class1();
then you can pass information to your class by doing
class1.size = textbox1.text;
inside you class add the following
public static string size { get; set; }
then all you need to call on the passed variable on form2 is
label1.text = class1.size;
hope this helps