In PCB relays, there are typically three kinds of contact types: single, single crossbar and twin crossbar. In the single contact type, the contacts hit each other in a wide surface area. This type of contact is used for applications requiring high capacity. Most PCB power relays have this contact type. In the single crossbar contact type, the contacts hit each other in a smaller point which helps to enhance contact reliability. This type of contact is found mainly in signal relays.  With twin crossbar contacts, the contacts hit each other in small points but with two movable contacts. Even if one movable contact is malfunctioning, the other contact should work. Omron uses twin crossbar contacts in some models as they provide high contact reliability.