The Side by Side Dovetail Plate - D & V Series by Losmandy:

This Losmandy Side by Side Dovetail Plate - D & V Series incorporates two saddle plates mounted parallel to each other. Used for mounting two optical systems side by side, by rotating the G-11 saddle 90 degrees. The Losmandy Side by Side Dovetail Plate - D & V Series accepts D and V series dovetail plates. The total weight is 7.25-pounds, total thickness 1.5-inches and Saddle plate separation is 10-inches, center to center.

OPT Product Number: LO-DVSBS