What brand of cable is this, and how is CAT6 only 300Mhz?

This is a U.S. brand, cat6 belongs to the gigabit cable but the frequency is only 300Mhz below to give you a comparison to see.

One of the different classifications: cat5e and cat6 are two different categories of cables, cat5e is categorized as a super category 5 cable, while cat6 is categorized as a category 6 cable. Although categorized differently, both work on the same principle and have the same type of RJ-45 plug and can be plugged into any Ethernet jack on a computer, router or other similar device.

Two, the difference in transmission bandwidth: Cat5e has a transmission frequency bandwidth of 100MHz, while cat6 has a transmission frequency bandwidth of 250MHz, which is a significant difference.

Three, the highest transmission speed and distance difference: Cat5e cable is used in Gigabit Ethernet, the transmission distance can be up to 100m, can support 1000Mbps transmission speed. cat6 cable can provide up to 10Gbps in 250MHz bandwidth. cat6 is most suitable for the application of 1Gbps transmission rate.

Four, the difference of using 10GBASE-T applications: Cat5e cable and Cat6 cable both have a transmission distance of 100m, but when using 10GBASE-T applications, Cat6 cable has a transmission distance of up to 55 meters.

V. Difference in transmission performance: Cat6 cables have an internal splitter that reduces interference or near-end crosstalk (NEXT), and it also improves far-end crosstalk (ELFEXT) compared to Cat5e cables, and has lower return loss and insertion loss.

Reference

Source: Baidu Encyclopedia - Network Cables (Classification)

cat5 100GbE cable