This is a TOMOCA 6.3φ monaural phone plug, L-shaped. The thickness is just under 10mm before cable soldering. The Soundhouse price at the time of listing was 150 yen per piece. https://www.soundhouse.co.jp/products/detail/item/79988/ I am selling this because I bought it but have no use for it. From a non-smoking, pet-free environment.