is an insert 407 the insert comprises a compensating chamber 409 at the top of which there is formed a cylindrical portion 410 which as can be seen from the cross section of fig1 forms a recess 411 inside the recess is a conical plug 412 having an arrowhead cross section extending from this cylindrical portion is a downwardly conically extending portion 413 and then a another conical portion 415 extending slightly outwardly following this is another conical portion 417 but now extending inwardly and forming a baffle this rests on a plurality of legs 419 which extend down to a portion of annular shape 421 having a u shaped cross section within this portion 421 there is thus formed an annular recess 423 as illustrated by the cross section of fig1 the annular cavity 423 receives the neck 403 of the container 401 on the outside wall of portion 421 are formed three projections 425 there is also provided an axially upwardly projecting part 427 on the end of which there is a tab 424 projecting radially outwardly during assembly the tab 424 of portion 421 is brought into abutment with the tab 405 at the base of the neck 403 and the two parts fastened together by gluing welding mechanical locking etc the final part of the syrup package is a cap like member 431 having an air inlet tube 433 extending upwardly therefrom the air inlet tube terminates in a conical portion 435 at the top 437 of the cap 431 in the closed position shown the top of the tube 433 seals externally against the recess 411 and internally against the arrowshaped.