error CS0122 in VS public sealed class ArrayBufferWriter<T>

Question

i want to use

public sealed class ArrayBufferWriter<T> : System.Buffers.IBufferWriter<T>

https://learn.microsoft.com/en-us/dotnet/api/system.buffers.arraybufferwriter-1?view=net-5.0

Compiler in VisualStudio gives me error CS0122

CS0122 Access to "ArrayBufferWriter " is not possible due to the degree of protection.

var outputBuffer = new ArrayBufferWriter< byte >();

Does anybody knows how to solve this error?