The 2inch nosepiece is precision machined with a straight sided barrel. This allows for more repeatable collimation in your 2" focuser or extension tube.
This avoids the collimation problems associated with "safety undercuts" on standard nosepieces.
A female M48x0.75 2" Astro filter thread on the front allows attachment of 2" filters
An ultra hard matte e-coat surface treatment gives more grip and durability. Internal threaded surfaces improve contrast.