European Motor Flange Sizes

I need to replace one make of motor with another and I’d like to find a reference to make sure I’m sending the correct numbers to the buyer who will be ordering the motor from the supplier. The frame size is 100LA4 and the flange size appears to be BM100, that’s the number stamped on the inside of the flange and I’d like to verify that it’s a standard number but haven’t found any good references online for flange sizes. I’m pretty sure about the frame size but I’d like to make certain of that as well.