Recent work demonstrates feasibility for ALS patients to communicate via P300 speller [1], but end-user's expectations are not met concerning comfort and ease of use, particularly for patient under heavy pathology [8]. One challenge for daily use [8],[9] is to provide patients with gel-free headsets that are easy to put on and comfortable while providing enough signal quality for accurate P300 classification. Our proposal is to custom design a silicone headset to fit patient's head morphology [5], paying attention on good pressure distribution and hair layer penetration. We will firstly show feasibility of Dry P300Speller with State-of-the-Art amplifier, then analyze electrode impedance variation over time while the headset is worn, and its relation to P300 classification accuracy.