Features: To keep water out and stop rusting from inside Easy and secure fitting Made from plastic Black colour All sizes measure in “mm” High quality product How to measure: Caps size is determined by the external diameter of the tube. pipe For example: external diameter (outside size) of tube 25mm then size of plugs=25mm The most common pipes have the following section - round. All plastic plugs are marked exactly like pipes. The outside dimension of the pipe corresponds to the marking of the plug. This is done so that the plugs can be easily selected according to the same size. Please if you not sure which size you need ask for help before you buy. if you need purchase many products. Contact me to get discounts.