Ko tā mātou pūmau tūnga whakarewa he taputapu matua hei āwhina i te aunoatanga whakarewa ahumahi, i hangaia hei arotau i te pai o te whakarewa, hei whakapai ake i te kounga whakarewa, hei whakaiti i te kaha o te mahi, ka waiho hei taputapu tino nui mo te hanga whakarewa, te tukatuka paipa, te hanga flange, me ētahi atu mara.
Mā te hoahoa hanganga matatau me te mahi pono, ka tū motuhake ia i te mākete, ā, ka tutuki i a ia ngā hiahia kanorau o ngā umanga iti, waenga me te nui.
Tuatahi, he tino tika te tūnga, me te tika o te tūnga anō o te ±0.1 ~ ±0.05mm, ka taea te whakarite tika i te mea mahi ki te tūranga pai rawa atu mō te whakarewa papatahi, te whakarewa miro rānei, kia kore ai e hapa pērā i te kore e uru pai.