Isikhli sesithathu sokuphindekela polyurethane kweShandong Tonda yindlela elishaya lokusebenza ngokubhebeka izinhlelo ezincane zokuphinda, ukuhlukanisa amathathu angcono. Isilayithi sasemva (Shore D 90) ususa ukusibekwa ngezinto ezingaphambili, isilayithi esesikati (Shore A 80) uhlobene nokushintsha nokuhlaba, kunye nekhetho lesisebenza (Shore D 70) uyihlobonzelo olungaphezu kohlaka. Ukulawula okuthile lokuphinda kuhlanganiswa ngokwesiphumo sokunquma emoneni, njengokocongqeleni nokukhombisa, ngokuvamile amasayizi amadifферent aphantsi kwiqhobo lasesithathu. Ngenxa yalokho, ukulawula kuhlanganiswa kunqume ukuthi amasayizi amadifферent aziphandele kwiqhobo lesotho lokusebenza. Phendulethu nomphendulo wakho ukubaleka iqinga lokusebenza lesithathu.