The Elite Pro line (133X) offers a memory grade for professionals who require higher write speeds and lower power consumption from their Compact Flash cards. This allows Elite Pro users the opportunity to get additional speed and performance.
Speed - 25MB/sec. read, 20MB/sec. write
For comparison of speed vs cost:
SanDisk Ultra II is - 9 megabytes (MB) per second and a read speed, 4GB - £20.99
SanDisk Extreme III is - Min 30MB/second sequential read and write, 4GB - £20.99
My new dSLR recommended the 133x, so it suits me.
Seems to be between £20 and £40 elsewhere.