The best sales to SMACO shop right now:

S300Plus 0.5l Mini Scuba Tank(for 5-10 mins underwater),

S400Pro 1l Scuba Tank(for 10-18 mins underwater),

S700 2l Scuba Tank(for 20-25 mins underwater),

Heap 1 High pressure electric air compressor(charge air by yourself for free at travel/home)...

And if you want a portable mini scuba tank but larger than the S300P, then you can choose the S500 0.7l mini scuba tank, what allows you to breath 12-15 mins underwater.