The Meade 07049 f/6.3 Focal Reducer & Field Flattener is a 4-element multicoated 41mm lens in a metal cell which threads upon the 2"-24 rear cell thread of any 8.0-16.0" Meade Schmidt-Cassegrain or Ritchey-Chretien telescope. It also is compatible with Meade's lineup of APO refractors and 7.0" Maksutov-Cassegrains(though not ideal for either, because they don't benefit from the field-flattening influence).
The Meade f/6.3 Focal Reducer & Field Flattener reduces the telescope's effective focal ratio by a factor of 0.63. Thus an f/10.0 Schmidt-Cassegrain becomes an f/6.3, an older f/6.3 becomes a f/4.0 and an f/8.0 Ritchey-Chretien becomes an f/5.0 system. With these drastic changes upon the telescope aperture, your exposure times will significantly shorten, making astrophotography easier.
The lens of the f/6.3 Focal Reducer & Field Flattener also improves the edge-of-field resolution of the telescope by flattening its field.