Axal Pro Water Softening Salt was recommended by the rep. for my Permutit Water Softener.
The tablets dissolve slowly retaining shape and integrity until completely gone so do not impede the flow of brine into the pick-up filter.
Hence my recommendation as an excellent product that does what the manufacturer
Other salt tablets I tried by me have crumbled and lost integrity forming a hard crust in the bottom of the water softener blocking the pick-up filter. Removal of this hard salt crust has been effected by emptying the softener and using hot water to dissolve the residue.