I think that is best for all those power tools marketing guys, them to stay away of getting involved by adding digital multimeter so their products catalogs them looking larger.
RYOBI TEK4 ( RP 4020 - 4V ) This is clearly multimeter engine build 25 years ago, this mainly translates to slowness of 1.5 or Max of 2 measurements per second (sampling speed).
Display digits of very low resolution, among with ugly over sided digits.
I have no idea of how this meter holds regarding compliance of true CAT III specifications.
ITTSB does not pass any positive recommendation about it, neither any one seeking for RYOBI TEK4 product review he will find any.
In the end of the day, they are much modern and reliably made meters for professional electricians in our days.
About such meters with low technical standards they could shown useful in the hands of a carpenter as voltage probe, but is this is your true expectation?
https://www.ryobitools.com/support/manuals/details/RP4020Now speaking of irregularities here is the major, this thing comes with Battery Pack (AP4001, 4 Volt
Li-ion)
This now explains of how
4V description this get mixed with product model description.
ITTSB Recommendation to RYOBI: Please remove this product from the market asap.
Li-ion batteries are famous for causing explosion due overheat. Certified multi meter's they can use exclusively ALKALINE