A coupling for joining pipe elements, said coupling comprising: • first and second segments (12, 14) positioned end to end surrounding a central space for receiving said pipe elements; • a spring assembly joining a first end of said first segment to a first end of said second segment, said spring assembly biasing said segments (12,14) away from one another; and • an adjustable attachment assembly joining a second end of said first segment to a second end of said second segment, said adjustable attachment assembly adapted to draw said first and second segments (12,14) toward one another and into engagement with said pipe elements, • wherein each of said first and second segments comprises: first and second channels (76, 78) positioned on opposite sides of said segments, each of said channels extending between said ends of said segments and having a first floor and a second floor facing said central space, said first floor having a greater radius of curvature than said second floor; first and second retainers positioned respectively in said first and second channels, each of said retainers comprising a band having oppositely disposed ends, a plurality of teeth being positioned along one edge of said band and projecting toward said central space, at least one tab being positioned along an opposite edge of said band, said band overlying said first floor, said at least one tab overlying said second floor when said retainers are positioned within said channels [claim 8]. • first and second segments (12, 14) positioned end to end surrounding a central space for receiving said pipe elements; • a spring assembly joining a first end of said first segment to a first end of said second segment, said spring assembly biasing said segments (12,14) away from one another; and • an adjustable attachment assembly joining a second end of said first segment to a second end of said second segment, said adjustable attachment assembly adapted to draw said first and second segments (12,14) toward one another and into engagement with said pipe elements, • wherein each of said first and second segments comprises: first and second channels (76, 78) positioned on opposite sides of said segments, each of said channels extending between said ends of said segments and having a first floor and a second floor facing said central space, said first floor having a greater radius of curvature than said second floor; first and second retainers positioned respectively in said first and second channels, each of said retainers comprising a band having oppositely disposed ends, a plurality of teeth being positioned along one edge of said band and projecting toward said central space, at least one tab being positioned along an opposite edge of said band, said band overlying said first floor, said at least one tab overlying said second floor when said retainers are positioned within said channels [claim 8]. first and second channels (76, 78) positioned on opposite sides of said segments, each of said channels extending between said ends of said segments and having a first floor and a second floor facing said central space, said first floor having a greater radius of curvature than said second floor; first and second retainers positioned respectively in said first and second channels, each of said retainers comprising a band having oppositely disposed ends, a plurality of teeth being positioned along one edge of said band and projecting toward said central space, at least one tab being positioned along an opposite edge of said band, said band overlying said first floor, said at least one tab overlying said second floor when said retainers are positioned within said channels [claim 8].