Convertible writing assemblies and components thereof

Convertible writing instrument assemblies are provided, including an outer barrel having a tapered nosecone with an aperture for a writing instrument tip and a grip portion, and an aperture for receiving an eraser or a push button therethrough, wherein the writing instrument assembly provides selective access to a volume defined by the outer barrel, and wherein the outer barrel and the volume are collectively configured to operably and interchangeably receive a mechanical pencil insert having the eraser and a retractable pen insert having the push button. Mechanical pencils and pens utilizing the convertible writing instrument assemblies are also provided, along with kits for providing such mechanical pencils and pens.