Hello, First of all, thank you for your interest in our product. For your height of 1.80 and weight of 65 kilos, size M will be suitable; considering your height, it will display a comfortable and standard posture on you. If you prefer the product to fit your body perfectly (slim fit), you can also consider size S, but in terms of general use and height ratio, size M would be a more ideal choice. If you have a different question, we would be happy to help. We wish you pleasant shopping. Madmext Team