A bucky is typically used for table or wall mounted x-ray systems and holds the x-ray cassette and grid. A bucky, is a device found underneath the exam table, a drawer like device that the cassette and grid is slid into before shooting x-ray.
The most common bucky size grids are 17 1/4 x 18 7/8, 17 1/4 x 17 3/4, and 18 x 18. Buckys are found in both medical and verterinarian offices.
There is nothing special about a bucky grid other than its size.
A reciprocating bucky is a device that moves the grid while the x ray is being taken. The motion keeps the lead strips from being seen on the image. The finer the lead strips, the less movement is needed.