A first firestop device and a second firestop device, each comprising a housing. The housing of the first firestop device has a connection side with a plurality of connection elements and the housing of the second firestop device has a complementary side with a complementary element. The connection elements are each arranged at a different location on the connection side of the housing of the first firestop device, so that a position of the first firestop device relative to the second firestop device, when the connection side of the housing of the first firestop device is interlocked with the complementary side of the housing of the second firestop device, is selectable by selecting which of the connection elements of the first firestop device is connected to the complementary element of the second firestop device.