diff --git a/motors/usb/queue.h b/motors/usb/queue.h
new file mode 100644
index 0000000..669abe4
--- /dev/null
+++ b/motors/usb/queue.h
@@ -0,0 +1,69 @@
+#ifndef MOTORS_USB_QUEUE_H_
+#define MOTORS_USB_QUEUE_H_
+
+#include <memory>
+#include <atomic>
+
+namespace frc971 {
+namespace teensy {
+
+// A FIFO queue which reads/writes variable-sized chunks.
+//
+// Reading data happens-after it is written. However, external synchronization
+// between multiple readers/writers is required.
+class Queue {
+ public:
+  Queue(size_t size) : size_(size), data_(new char[size]) {}
+
+  // Writes as much of in_data as will fit to the queue. Returns the number of
+  // bytes written.
+  size_t Write(const char *in_data, size_t in_size);
+
+  // Reads up to out_size from the queue into out_data. Returns the number of
+  // bytes read.
+  size_t Read(char *out_data, size_t out_size);
+
+  size_t data_queued() const {
+    return space_used(read_cursor_.load(::std::memory_order_relaxed),
+                      write_cursor_.load(::std::memory_order_relaxed));
+  }
+
+  size_t space_available() const {
+    return size_ - data_queued() - 1;
+  }
+
+  bool empty() const {
+    return read_cursor_.load(::std::memory_order_relaxed) ==
+           write_cursor_.load(::std::memory_order_relaxed);
+  }
+
+ private:
+  size_t space_used(size_t read_cursor, size_t write_cursor) const {
+    size_t r = write_cursor - read_cursor;
+    if (r > size_) {
+      r = size_ + r;
+    }
+    return r;
+  }
+
+  size_t wrap(size_t cursor) const {
+    if (cursor >= size_) {
+      return cursor - size_;
+    } else {
+      return cursor;
+    }
+  }
+
+  const size_t size_;
+  const ::std::unique_ptr<char[]> data_;
+
+  // The next index we're going to read from.
+  ::std::atomic<size_t> read_cursor_{0};
+  // The next index we're going to write to.
+  ::std::atomic<size_t> write_cursor_{0};
+};
+
+}  // namespace teensy
+}  // namespace frc971
+
+#endif  // MOTORS_USB_QUEUE_H_