This plate is similar to the SB3622, however the additional 5" of length make it a great choice for extra-long instruments or side-by-side configurations. Our own experience mounting our prototype 305mm f3.8 Riccardi-Honders and 305mm f12.5" Maksutov-Cassegrain pointed out the need for a longer plate. Hole spacings include: 3.2"-3.5" slot, 3.937", 4.5", 4.921" 5.5", 6.875", 7.450"and 8.220" to accommodate an even wider variety of instruments. They are repeated throughout the length of the plate. Suitable instruments include: All rings with the Astro-Physics hole pattern, 305mm f3.8 Riccardi-Honders, and large Takahashi instruments. The DOVELM162 can be bolted on for side-by-side configurations as mentioned above.