1Functional Design: Provides extra focusing distance to increase focal length extension. Sometimes necessary for certain eyepiece or telescope camera combinations for focusing. 2Extended Focusing Needed: Often requires more focusing distance when observing short distances on the ground with a telescope or using field flatteners, correctors, or reducer lenses. 3Secure Connection: Equipped with 2 fixed screws to support connecting 2 inch telescope eyepieces and astrophotography filters, preventing damage to telescope accessories. 4Universal Compatibility: Features front end with M48x0.75mm thread for use with 2 inch telescope eyepieces and astrophotography filters, ensuring a secure fit. 5Sturdy Construction: Anodized black finish prevents unnecessary reflections. Made of solid aluminum alloy material for strength, durability, and wear resistance. 1 x Extension Tube