This device allows a range of USB peripherals to be used on the Sega Dreamcast, such as mouse, keyboard, driving wheel and many various game controllers 
USB4MAPLE has a VMU emulation feature that allows you to save games to a FAT-32 formatted flash drive if you have one plugged in via a USB splitter or hub.
There is 2 different options
Option 1 - Single USB port
Option 2 - Dual USB port splitter. The splitter is to plug in a usb flash drive for a virtual VMU
The device works with the following but not limited to these devices (for instance most all usb mouse and keyboards should work)
Adapters
GP2040-CE Fighting Board
Mayflash GameCube Controller Adapter
Mayflash Magic-NS 2
Mayflash Magic-NS Lite
Mayflash Magic-S Pro 2
Mayflash Sega Saturn Controller Adapter
PlayStation 1/2 Twin USB Adapter
Smart Joypad PS1/PS2 USB Adapter
Raphnet N64/GameCube to USB adapter V3
Arcade Sticks
Astro City Mini Arcade Stick
ChImp PC PS3 Controller
Hori Fighting Stick 3
Hori RAP VX SA
Hori Real Arcade Pro 3 SA
Hori Real Arcade Pro 4
Hori Wireless Fighting Stick 3
Hori Xbox 360 Dead or Alive 4 Arcade Stick
MayFlash Arcade Stick F101
MayFlash Arcade Stick F300
Mad Catz Arcade Fight Stick MS
Mad Catz Arcade Fight Stick Tournament Edition
Namco PlayStation Arcade Stick (w/ PS1 adapter)
NEOGEO Arcade Stick Pro
PowerA Fusion Wireless Arcade Stick
Qanba Obsidian
Qanba Q4RAF
Razer Panthera
Toodles Kitty TE
Controllers
8BitDo M30 Controller (in DInput mode)
8BitDo Micro Gamepad
8BitDo Mod Kit for Original MD Controller
8BitDo N30 Bluetooth Controller
8BitDo NEOGEO Controller
8BitDo Pro 2 Controller (in DInput mode)
8BitDo SNES30
8BitDo Ultimate 2.4G Controller (in DInput mode)
Amazon Luna Controller
Betop BEITONG Fighting Gamepad BTP-C3
Densha De Go! Controller Type 2 (PS2)
Gamesir Tegenaria Lite
Google Stadia Controller
GuliKit KingKong 2 Pro Controller (Android/iOS mode)
HORIPAD 3 Turbo
HORIPAD Switch Controller
HORIPAD Mini Switch Controller
Hori Pokken Tournament Pro Pad (works as arcade stick)
iBuffalo Classic USB Gamepad
Mad Catz Modern Warfare 3 Xbox 360 Controller
Mad Catz Street Fighter X Tekken FightPad SD (PS3)
PlayStation 2 Controller (Official) (w/ PS2 adapter)
PlayStation 3 Controller (Official)
PlayStation 3 Controller (KAPBOM brand)
PlayStation 4 Controller (Official)
PlayStation 5 DualSense Controller
PlayStation Classic Controller (works as arcade stick)
PowerA Enhanced Wired Controller (Switch)
Retro-Bit Legacy16 Wired Controller
Retro-Bit Sega Saturn USB Controller
Saturn USB Play Sega Controller
Sega Astro City Mini Gamepad
Sega Mega Drive Mini Controller
Speedlink TORID Wireless Controller
Thrustmaster eSwap Pro
Xbox 360 Controller (Official) (wired or wireless with a wireless receiver)
Xbox 360 Controller (Shengan brand)
Dance Mats
PlayDance DDR Dance Mat
Joysticks
Gembird JSK-420
Logitech Extreme 3D Pro
Logitech Force 3D Pro
PXN-F16
Keyboards
Corsair Vengeance K65
Dell KB216
Dell Pro KM5221W
Hexgears X5
Logitech G613
Logitech K400 Plus
Logitech K400R
Logitech K845
Logitech MK295 (keyboard only)
Microsoft Digital Media Pro
Phantasy Star Universe Wireless Keyboard
TECKNET TK-KB004
ThundeRobot K104
Mice
Logitech M170 / M171
Microsoft Basic Optical Mouse 2.0
Microsoft IntelliMouse Explorer 3.0
Uineer Wired Mouse
Razer Viper Mini
Razer Viper v2 Pro
Zowie EC1-CW
Racing Wheels
HORI Mario Kart Racing Wheel Pro Deluxe
Logitech Driving Force
Logitech Driving Force Pro
Logitech Driving Force GT
Logitech G25 Driving Force
Logitech G27 Driving Force
Logitech G29 Driving Force (in PS4 mode)
ThrustMaster Ferrari GT Experience
Xbox 360 Wireless Racing Wheel (with wireless receiver)
Xbox 360 Wireless Speed Wheel (with wireless receiver)