The ZWO Mini Guide Scope is compatible with all ZWO ASI cameras.  The aperture is 30 mm and the focal length is 120 mm, making it an f/4 system.  It is perfect go guide on telescopes with a focal length of less than 500 mm.  

The guider ring of the ZWO 30F4 has M42 x 0.75 threads that terminate to an 1.25" opening.  To focus the Mini Guide Scope just turn the front barrel.  Focus can be locked with the red ring so you only need to focus once.

The guide scope slips into the included guide ring - use the knurled knobs to lock it in place.  A dovetail foot attaches to the guide ring and has a 1/4-20 screw hole for attachment.  If you'd like to use the guide scope by itself, it can be removed from the guide ring/foot.

Specifications:

• Aperture:  30 mm
  
• Focal Length:  120 mm
  
• Focal Ratio:  f/4
  
• Weight:  250 g 
  
• Back Focus:  Adjustable from 0-20mm
  
• Tube Travel:  20 mm