The Combo A1 adapter kit from QHY is compatible with the QHY294M / 163M, QHY CFW3M-S, and QHY OAG. All of the items in this kit are to be used with a 55mm BFL MPCC. This kit is included as a standard accessory with the QHY294M.
QHY took customer feedback and used it to create a fixed combination of adapter kits to meet the mainstream needs of most users. Since QHY offers so many adapters, there is a variety of back-focus distances that can be intimidating and confusing to new users. Users requested adapters that would provide 55mm of back focus, which is the perfect amount of back focus for astrophotography, in order to accommodate commonly available optical systems with field flatteners / correctors.
NOTE: If users do not have any special requirements for back focal length, you can use a standard T-mount. This kit is designed for those that need a specific back focal length.