The highest commonly available speed for SFP (Small Form-Factor Pluggable) transceivers is 25 Gigabits per second (25 Gbps). These transceivers are referred to as SFP28 (SFP+ for 25 Gbps) and are used in high-speed networking applications, including 25 Gigabit Ethernet (25GbE).

SFP28 transceivers provide a higher data rate compared to the earlier SFP and SFP+ modules, which typically supported speeds up to 10 Gbps. SFP28 modules have the same physical form factor as SFP+ modules but are designed to operate at the higher data rate of 25 Gbps.

It's worth noting that advancements in networking technology may result in higher-speed transceivers in the future. For example, there are also QSFP28 (Quad Small Form-Factor Pluggable 28) transceivers that support even higher speeds, such as 40 Gbps and 100 Gbps. QSFP28 is a larger form factor than SFP28 and is commonly used for higher-speed applications in data centers and telecommunications networks.

For the latest information on SFP transceivers and their supported speeds, it's recommended to check with the specific manufacturers and refer to their product documentation or datasheets. The networking industry continues to evolve, and higher-speed transceivers may become more prevalent with ongoing advancements.