referring to the drawing and fig1 and 3 in particular shown therein generally designated by the referenced character 10 is a curing envelope that is constructed in accordance with the invention as shown most clearly in fig1 the curing envelope 10 is an annular member of generally u shaped cross sectional configuration see fig3 the envelope 10 includes an outer circumferential surface 12 an inner circumferential surface 14 and a pair of sidewalls 16 and 18 preferably the envelope 10 is constructed from a flexible elastomeric material that is sufficiently flexible to be applied over a tire carcass and that can withstand the heat required for curing the rubber retread material one such material is bromobutyl rubber manufactured by exxon chemical an air or gas flow passageway 20 extends through the curing envelope 10 in alignment with the flow passageway 20 is a hollow valve stem 22 the valve stem 22 may be provided with appropriate valving not shown the inner circumferential surface 14 of the envelope 10 is provided with a plurality of lands 30 that are spaced apart to provide a plurality of flow passages 32 therebetween which are in communication with the flow passageway 20 preferably there are about 100 lands 30 per square inch the lands 30 are enlarged for clarity in the drawing each of the sidewalls 16 and 18 terminates in a sealing edge portion 26 and 28 located adjacent to the annular sealing edges 26 and 28 are a plurality of annular striations 34 and 36 which provide sealing lands 38 and 40 which sealingly engage the side wall of a tire carcass 42 see fig5 fig4 and 5 are views of a tire carcass.