A union for coupling two or more segments (11, 11') of tubing or optical fiber, comprising a) an elastomeric core (2, 16) having one or more linear or branched tubular sections, each having an internal bore, which, when more than one tubular section is present, is in fluid or optical communication with the internal bores of the other tubular sections, b) a union body having a through bore for each of said one or more tubular sections, which girdles said tubular section or sections, the size and shape of said through bore or bores of said union body being complementary to the size and shape of the tubular core section girdled by each and the dimensions of said through bore or bores of said union body approximating but exceeding the outside diameter of the corresponding tubular core section, so as to substantially prevent outward radial expansion of said tubular core section or sections, c) a housing having at least one through bore with an inlet and outlet, d) compression elements engagable with said housing to impart an axial compression upon said elastomeric core (2, 16) when the through bore or bores of said union body is or are aligned with said through bore or bores of the housing, whereby upon insertion of segments (11, 11') of tubing or optical fiber having an outside diameter which approximates or is less than the internal diameter of said bore or bores of said section or sections of elastomeric cores (2, 16) into said bore or bores of said elastomeric core section or sections and axial compression of said elastomeric core section or sections by said compression elements in combination with the prevention of radial outward expansion of said elastomeric core section or sections by said bore or bores of said union body, an inward radial compression is imparted to said elastomeric core section or sections to sealingly engage said segments (11, 11') of said tubing or optical fiber, characterised in that said at least one bore of the housing being interrupted by a recess in said housing having a size and dimensions to accommodate the removable insertion of said union body and to align said elastomeric core (2, 16) or cores of said union body with the through bore or bores of said housing upon insertion of said union body into said recess, the recess is substantially orthogonal to said at least one through bore, having a depth sufficient to penetrate said at least one through bore. a) an elastomeric core (2, 16) having one or more linear or branched tubular sections, each having an internal bore, which, when more than one tubular section is present, is in fluid or optical communication with the internal bores of the other tubular sections, b) a union body having a through bore for each of said one or more tubular sections, which girdles said tubular section or sections, the size and shape of said through bore or bores of said union body being complementary to the size and shape of the tubular core section girdled by each and the dimensions of said through bore or bores of said union body approximating but exceeding the outside diameter of the corresponding tubular core section, so as to substantially prevent outward radial expansion of said tubular core section or sections, c) a housing having at least one through bore with an inlet and outlet, d) compression elements engagable with said housing to impart an axial compression upon said elastomeric core (2, 16) when the through bore or bores of said union body is or are aligned with said through bore or bores of the housing,