The Pilot Custom K series of pens, released in 1971, consists of three pens, each created to look different but with the same intent. The pens can be found as a stainless steel pen with black chrome stripes running along its body down to the nib (K-500SS), a sterling silver pen with a checkered body (K-1000SS), and a pen created with gorgeous wood from painted maple trees (K-500KS). These different styles of pens were created to give a sense of individuality to each person who bought one, and they continue to live up to their duty today. The Custom series grew to be one of the most popular Pilot fountain pens and has been produced in a variety of styles and finishes. It is these three pens that started the line.

Specs below are for the fountain pen.

- Manufacturer/Model: Pilot Custom K-500SS Stainless Steel
- Year: Hiratsuka Factory, October 1974
- Color: Silver, black stripe
- Material: Stainless Steel
- Nib: 18k Gold. Fine
- Filling System: Cartridge/Converter
- Condition: Good. All Pens show minor but obvious signs of wear. Moderate scratches and scuffs on the barrel and cap of the fountain pen but overall in good condition. The ballpoint pen does stick sometimes when clicking. 
- Warranty: 90 days
- Made in Japan

Measurements
- Length capped: 135 mm
- Barrel length inc nib: 123 mm
- Cap length: 64 mm
- Barrel diameter: 11 mm
- Section diameter: 10 mm