Hi,
I have the Aluminum Caps (
http://eagleday.stores.yahoo.net/exac4.html ) and like them alot. They are full length and were designed for the 993 Turbo in order to eliminate the Valve Stem Support. They are a cap and support in one.
They stand out less and so some kid isn't as likely rip them off for his bike as happened twice on my Esprit - only 2 stolen at a time until I replaced them with the Tamper-proof ones...
Happy Motoring!... Jim'99