This is a Tasco/Celestron 4.5" mirror cell that has been carefully modified to hold a standard Edmund 4.25" mirror. If you have wanted to replace the spherical primary mirror in one of the little "short tube" department store reflectors with decent optics, this cell will make the job a lot easier. As a "drop in replacement," it exactly fits the tubes of most (if not all) Tasco models, the older Celestron 4.5 reflectors, and many of the newer Celestron scopes that are similar to the Tasco line. [This cell will NOT fit Meade tubes, as they are of a slightly different diameter. I am not sure if it will fit Orion products.]
As shown in the photo [4.25" mirror set not included], it comes with all the inserts and clips to exactly fit your 4.25" Pyrex mirror. To do the conversion properly on this cell takes a bit more time and machining than you might think, so the time saved by buying one is not trivial.
Asking $15.00, plus $4.00 for priority postage, or will trade for a decent quality used 1.25" star diagonal.