Condoms, as one of the common daily contraceptive measures, need to pay attention to the size of the condom when choosing, the condom size is large is likely to risk falling off, or even lead to contraceptive failure; while the size is small may be too tight to produce discomfort, but also may rupture. Therefore, only when you choose the right condom, you can get sexual satisfaction and at the same time achieve the maximum contraceptive purpose. So, how do we choose condoms? First of all, we need to know what condom sizes are available! Condom specifications can be divided into large, medium, small, and extra small according to the nominal width, the nominal width refers to half of the circumference of the condom opening. 1, large condoms: nominal width of 55 mm, perimeter 110 mm, diameter of the opening is 35 mm; 2, medium condoms: nominal width of 52 mm, perimeter 104 mm, diameter of the opening is 33 mm; 3, small condoms: nominal width of 49 mm, perimeter 98 mm, diameter of the opening is 31 mm; 4, small condoms: nominal width of 48 mm, perimeter 96 mm, diameter of the opening is 31 mm; 4, small condoms: nominal width of 48 mm, perimeter 96 mm, diameter of the opening is 31 mm. The circumference is 96 mm, and the diameter of the opening is 29 mm. How to do accurate measurement and choose the right condom for you? 1, nominal width measurement: men can use a thin wire, around the middle of the penis after a full erection, and then measure the length of the wire, the result is the penis circumference value, divided by 2 to get the nominal width; 2, diameter measurement: diameter measurement also need to use a thin wire, around the middle of the penis after a full erection, the measured length of the thin wire divided by 3.14, to get the diameter. Do I need to measure the length of the condom? It is not necessary to measure the length, because the width of the condom is more important than the length. Condoms are manufactured with a large space for expansion and contraction, and as long as they can adequately cover the head of the penis and ensure that semen does not escape, there is no need to consider the length of the condom. Condoms need to be selected according to the nominal width and diameter of the individual’s penis, if the individual cannot be accurately measured, the most common condom on the market can be chosen medium, that is, the nominal width of 52 mm, and then adjusted according to the size of their own wearing situation. If there is a feeling of wrapping and binding at the penis when using a medium condom, but no tightness or poor blood flow, it is the right size. If there is loosening or falling off, it is recommended to buy a small one; if the excessive tightness of the binding, affecting the blood flow, or even ejaculation, it is recommended to buy a large one.