There are three models of QHYOAG: QHYOAG-S, QHYOAG-M, and QHYOAG-L for different size sensors. The QHYOAG is a thin and solid design. The OAG main body is just 10mm thick. Adding an M42 thread or M54 adapter ring adds only 3mm for a total thickness of 13mm. There are six 3mm through holes in the OAG for direct connection to the QHYCFW2 and QHY "A" series cameras. If you do not have a QHYCFW2 or QHY "A" series camera, you can also use this OAG with a third-party adapter ring on the camera side. The QHYOAG comes with a multithread 1.25-inch focuser. The focuser has a locking thumbscrew to hold the guide camera fixed after focusing. The prism position can be adjusted and can be locked to fix its position. The prism is 8mm x 8mm size and the aperture between the prism and mirror is 8mm in diameter.