Hi @user-9a1aed , I am not sure I fully follow, but to get the number of fixations and fixation duration, you do not need to join gaze.ts and fixations.ts.

Our fixation detector has already done all the hard work for you.

You only need the following Python code:

# number of fixations in recording
n_fixations = len(recording.fixations)

# duration of each fixation (in nanoseconds)
fixation_durations_ns = [(fix.end_ts - fix.start_ts) for fix in recording.fixations]