Closures for laboratory glassware

Claim 1

A CAP-LIKE CLOSURE FOR OPEN-ENDED TUBES, SAID CLOSURE BEING FORMED OF A SOMEWHAT RESILIENT RUBBERY MATERIAL AND COMPRISING A TUBULAR SKIRT OPEN AT ONE END AND CLOSED AT THE OTHER, SAID SKIRT HAVING A CYLINDRICAL SIDE WALL WHICH IS PROVIDED WITH A STRAIGHT CYLINDRICAL INWARDLY PRESENTED INTERNAL FACE, SAID SIDE WALL BEING PROVIDED AROUND ITS INTERNAL FACE WITH AXIALLY EXTENDING INWARDLY PROJECTING FLEXIBLE FINS WHICH ARE INITIALLY AND PERMANENTLY CURVED LATERALLY WITH RESPECT TO A RADIAL PLANE EXTENDING THROUGH THE LINE OF ATTACHMENT BETWEEN EACH FIN AND THE SKIRT SO AS TO BEAR TANGENTIALLY AGAINST THE TUBE TO WHICH THE CLOSURE IS APPLIED, SAID CLOSED END BEING PROVIDED ON ITS INTERIOR FACE WITH AN ANNULAR GROOVE HAVING A FLAT TRANSVERSE FACE FOR SNUG-FITTING PLANAR ABUTMENT AGAINST THE MOUTH OF SAID TUBE, SAID FINS EXTENDING FROM THE BASE OF THE GROOVE AND TERMINATING A SHORT DISTANCE ABOVE THE LOWER MARGIN OF SAID SKIRT, SAID FINS HAVING A RELATIVELY CONSTANT THICKNESS FOR A GREATER PORTION OF THEIR AXIAL LENGTH AND BEING TAPERED AT THEIR LOWER ENDS OUTWARDLY AWAY FROM THE LONGITUDINAL CENTER-LINE OF THE CAPLIKE CLOSURE, SAID CLOSED END ALSO HAVING A DOWNWARDLY EXTENDING CONCENTRIC CYLINDRICAL BOSS HAVING A DIAMETRAL SIZE SUBSTANTIALLY SMALLER THAN THAT OF THE INSIDE DIAMETRAL SIZE OF THE OPEN END OF THE TUBE OVER WHICH THE CAP-LIKE CLOSURE FITS INTO THE MOUTH OF SAID TUBE, WHEREBY THE UPPER PORTION OF THE CAP-LIKE CLOSURE MAY SHIFT SLIGHTLY IN THE TRANSVERSE DIRECTION WITH RESPECT TO THE OPEN-ENDED TUBE UNDER IMPACT WHILE SUBSTANTIALLY MAINTAINING THE CLOSURE-FORMING ENDWISE ABUTMENT BETWEEN THE FLAT BOTTOM FACE OF THE ANNULAR GROOVE AND THE MOUTH OF SAID TUBE.