Both the Tab S 8.4 and Tab S 10.5 have their own Book Cover and Simple Cover, but it looks like only the larger 10.5-inch tablet can use the Bluetooth Keyboard.
The Galaxy Tab S Book Cover allows you to position your slate in three different angles: viewing mode, touch mode, and typing mode. It’ll be offered in the following colors: white, black, bronze, ivory, red, and blue. The Simple Cover provides “the same protective structure of the Book Cover, but with a slimmer design.” This will be available in white, black, bronze, red, and blue.
As for the Bluetooth Keyboard, this transforms the Galaxy Tab S 10.5 into a laptop. It's lightweight and thin (340 grams, 7.5 mm), being made "from identical materials" as the tablet itself. The keyboard features Bluetooth 3.0, 80 keys (including specific hotkeys), and a rechargeable 200 mAh battery.
Samsung also said that its Level headphones are compatible with the new Tab S slates - but we’ve seen these before, when they were first unveiled back in April.