Bronson L-Theanine 200mg (Double-Strength) with Passion Flower Herb, Non-GMO Gluten-Free Soy-Free Stress Management Supplement, 360 Capsules

Vegetarian cellulose capsules take longer to break down, in general, as compared to gelatin capsules that dissolve almost immediately. The strongest encapsulated theanine is probably this one: https://www.amazon.com/dp/B07S5GD29K and this is what I use currently, for a few years now. (But I'm one of those that requires larger amounts of theanine for effect.) I have also used this item: https://www.amazon.com/dp/B07DGK6JY7 and the addition of a small amount of passion flower does seem to have a palpable benefit.