A sliding sleeve opening with a deployed plug (B), comprising: a housing defining a first bore and defining a flow port communicating the first bore outside the housing ; an inner sleeve defining a second bore and being movable axially inside the first bore from a closed position to an opened position relative to the flow port ; and a seat disposed in the sliding sleeve and having a top end and a bottom end, the seat comprising a plurality of segments , the segments expanded to an expanded state with a first internal dimension in a first axial position inside the first bore of the housing , the first internal dimension of the segments of the seat configured to initially pass one or more first of the deployed plugs (B) deployed through the seat in the first axial position and configured to engage a second of the deployed plugs (B) deployed in the seat in the expanded state of the first axial position, the seat engaged with the second plug (B) being moveable axially from the first axial position in the first bore of the housing to a second axial position in the second bore of the inner sleeve in response to fluid pressure applied against the second deployed plug (B), the segments contracting inward to a contracted state in the second axial position inside the second bore of the inner sleeve with the bottom ends of the segments of the seat transitioning from the first internal dimension to a second internal dimension before the top ends of the segments of the seat transition from the first internal dimension to the second internal dimension, the second internal dimension being less than the first internal dimension; the top ends of the segments wedging the second plug (B) in the seat as the top ends transition and subsequently compress inward toward the second internal dimension about the second plug (B), and the inner sleeve moving from the closed position to the opened position with the seat engaged with the second plug (B) in the second axial position. a housing defining a first bore and defining a flow port communicating the first bore outside the housing ; an inner sleeve defining a second bore and being movable axially inside the first bore from a closed position to an opened position relative to the flow port ; and a seat disposed in the sliding sleeve and having a top end and a bottom end, the seat comprising a plurality of segments , the segments expanded to an expanded state with a first internal dimension in a first axial position inside the first bore of the housing , the first internal dimension of the segments of the seat configured to initially pass one or more first of the deployed plugs (B) deployed through the seat in the first axial position and configured to engage a second of the deployed plugs (B) deployed in the seat in the expanded state of the first axial position, the seat engaged with the second plug (B) being moveable axially from the first axial position in the first bore of the housing to a second axial position in the second bore of the inner sleeve in response to fluid pressure applied against the second deployed plug (B), the segments contracting inward to a contracted state in the second axial position inside the second bore of the inner sleeve with the bottom ends of the segments of the seat transitioning from the first internal dimension to a second internal dimension before the top ends of the segments of the seat transition from the first internal dimension to the second internal dimension, the second internal dimension being less than the first internal dimension; the top ends of the segments wedging the second plug (B) in the seat as the top ends transition and subsequently compress inward toward the second internal dimension about the second plug (B), and the inner sleeve moving from the closed position to the opened position with the seat engaged with the second plug (B) in the second axial position. <EOS>