What the 90 Ohm impedance means on a signal line
The ACM2012H-900-2P-T05 is a 2-line common mode filter from TDK's ACM-H series, rated 90 Ohms at 100 MHz. That impedance peak is where it knocks down common-mode noise on a differential signal pair — think USB, CAN, or LVDS lines running inside a tight enclosure where the filter sits right at the connector. The 300 mA current rating and 20 VDC voltage rating tell you this is a signal-line filter, not a power rail part; put it on the data pair, not the supply.
Board-fit and handling on site
It comes in an 0805 SMD package (0.079" x 0.047", 1.30 mm max height) with a 4-pad horizontal layout — orientation is clear from the pad pattern, so you can swap it in the field with a standard hot-air station and tweezers. No special ESD bench needed; just watch the polarity mark on the package if there is one (some common-mode filters are symmetric, but check the part marking).
Still in production and how to get it
It is a standard catalog part, so supply is steady through distribution. No pin-compatible second source is documented, but the 0805 common-mode filter footprint is widely used; if you need an alternative, the closest parametric match would be another 2-line 0805 filter with similar impedance and current rating from a different brand.