strong stellar winds. From here on, this structure of 20$\times$9 in size (14.5$\times$6.6 pc at 2.5 kpc), will be referred to as G353.12+0.86, being Shell A its molecular counterpart.

The molecular hydrogen column density $N_{H2}$ and the molecular mass associated with Shell A and cloud B were estimated from the $^{12}$CO data, making use of the empirical relation between the integrated emission $W_{CO}$ ($\equiv \ \int T dv)$ and $N_{H2}$. We adopted $N_{H2}$ = (1.9$\pm$0.3) W$_{CO}$ $\times$ 10$^{20}$ cm$^{-2}$ (K )$^{-1}$, obtained by @murphy91. The amount of molecular gas in Shell A between $-$7.5 and 0  is (1.2 $\pm$ 0.6) $\times$10$^5$ , while for Cloud B, we derive (3.4 $\pm$ 1.7) $\times$10$^3$   taking into account the emission in the range \[$-$12.5,$-$7.5\] . Velocity intervals and H$_2$ masses of the clouds identified in NGC6357 are listed in Table 2.

In the following paragraphs we analyze in some detail the characteristics of this structure.

Morphology and characteristics of G353.1+0.86
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The central cavity of G353.12+0.86 shows diffuse  emission revealing that it is filled by hot gas at T $\approx$ 10$^4$ K. The / ratio derived for the cavity (in the range $\approx$ 0.09-0.12, Fig. 4) indicates a region with high excitation conditions. 