This A/B/Y is arguably the best available. It is True-Bypass, solidly built, properly grounded, and very good looking. It works well to switch to one amp, the other amp, or both amps together. Hum free, bleed free, and pop free design. The standard ABY configuration is horizontally oriented, as pictured. This includes the "Both" LED indicator, which lights when both outputs (A&B) are selected. This convenient update allows the user to know which output will be on when the A/B operation is selected. (For example, if you are using "A", the "A" LED would be lit. Then, by pressing "A&B", the "Both" LED would also light up, indicating that both outputs are on. Then, if you pressed "Both" again, you would return to the "A" LED and "A" output being on).
The ABY uses the "B" size enclosure. It measures 4.4 x 2.4 x 1.0 inches; 11.3 x 6.1 x 2.5 cm.