My previous Yamaha mount block was from a first generation DTX (from the late 90s) - I continued to use that block for a while, as the holes still fit Yamaha / Roland modules (indeed, the holes still fit the DTX Multi 12 that I purchased the new MAT-1 for). The old model had the tom arm enter vertically (perpendicular to the "face" of the module / multipad), while this model has the tom arm enter horizontally (parallel to the "face").
This change makes the mounting block _much_ more flexible in terms of positioning -- the tom arms can be used in their "natural" state, with the main tube of the tom arm positioned vertically. However, it does introduce one issue -- now, the wingnut on the top of the tom arm can potentially interfere with the module that you're mounting. For example, on the DTX Multi-12, you need to use the "full-sized" tom arm to mount the pad -- the short-armed ("YESS mount") Yamaha tom arm doesn't allow the wingnut to clear the bottom of the DTX. It's not a deal-breaker, certainly, it just means you need to be careful with your combination of hardware.
One other thing that I was wondering about before making the purchase -- although it looks like there is a "keyhole"-style hole, allowing for easy removal of the mounting block, it's not actually the case. The block still attaches to the module/multipad via 4 normal screws, and you need to unscrew / remove all four of the screws to remove the block. Again, not a deal-breaker, but just something that I wanted to point out.
