The SMS1145 Swedish Standard Union and also the Danish Standard Union both incorporate a round slotted nut and feature a square section seal. More recently the SMS1149 lipped seal has been introduces to enhance the cleanliness of the union’s interface. The union is suitable for use on permanently fitted sections of pipework and is generally unforgiving on misaligned joints. The fitting does have the advantage over other designs in that it facilitates the removal of sections of pipework without the need to disturb adjacent sections.