If you own some version of the popular 4.5" f/8 (114 x 900 mm) reflector that has been so widely marketed in recent years, you may have discovered that it is light and easy to use, but has pretty marginal optics.
If you are lucky, your primary is at least a good sphere, but there are a lot of them out there with astigmatism and dog-biscuitey surfaces. [I've seen lots of these, unfortunately!]
I recently was given a 4.5" f/8 mirror that -- unlike most -- appears to be at least partially corrected and shows a nice smooth surface on the test stand. [NOTE: I have not attempted to do accurate zonal measurements on this mirror, but it looks good in a qualitiative way.] Based on other mirrors that I have examined, this one appears to be much better than most. The "down side" of this one is that the coating is not perfect, there being some fine abrasions, but this should not adversely effect seeing.
Am offering this one for $35.00 (plus shipping) on a "try it out" basis. If you've got a bad primary mirror [and the diagonal isn't the problem -- which it often is!] and this one isn't significantly better, then I'll refund your money on return of the mirror.
Thanks and Clear Skies --