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Never use pyrex to measure your lye or raw soap in. Over time, the lye creates microscopic cracks and your pyrex with the lye or raw soap could shatter.
Rastaurant supply places like Smart & Final carry heavy duty, large plastic containers which can be used for lye or to mix your soap in. I use a stick blender to mix, plastic spoons with long handles and silicone spatulas. You can use stainless steel, just make sure that it's true stainless steel. I don't use any specific brands, as some of the utensils can be found at the Dollar store.
The stick blender I have, which is a Braun, with a detachable stainless steel shaft is not made any more, so I'll leave this question for someone else to answer.
You might also read this sticky I posted>
viewtopic.php?f=2&t=3800