Eyepiece Parfocalising rings allow you to set the focus register of your eyepieces so accurate that you can change the eyepiece so rapidly without the need for refocused. Ring are available either as singles unit or, in the case for more popular 1.25" eyepiece, a set of four can be added. The single-ring kits are supplied with fitting key and spare grub screw. The rings are precision-manufactured from aluminum, and are silver or self-colour finish