Ultimate Credit-Card Key Holder | Whistle, Pen

Credit-Card Key Holder with Whistle and Optional Toothpick and Pen

This model is a compact, wallet-sized key holder designed in the format of a standard credit card. It allows you to carry your house key securely and comfortably inside your wallet without adding bulk. The design includes three size variants to accommodate different key sizes, ensuring that almost any standard key can be stored inside.
(If your key does not fit, please leave a comment including the diameter of the key head and the key thickness.)

Integrated Features

• Wallet-sized Key Holder: Keeps your key flat and protected inside your wallet.
• Loud Emergency Whistle: Integrated directly into the card body for additional functionality.
• Optional Toothpick & Pen Version: A second version includes slots for a reusable toothpick and a slim pen.
  • If you print the pen version, you will need a 70 mm × ~2 mm pen refill. One suitable example is:
    10pcs 70 mm Ballpoint Refill (70 mm × ~2 mm) — a pack of 10 short 70 mm refills (sized ~2mm diameter) suitable for international purchase.
    (Note: this is sold as an “international short refill”, so it supports the intended 70 mm × 2 mm specification.)
    For further alternatives, there are other short refills (70 mm length) available from international suppliers. eBay+1

Available Versions & Key-Size Variants
There are three key-slot size variants corresponding to different key head diameters and thicknesses:

• Variant A: For key heads Ø > 19 mm, thickness < 2.8 mm
• Variant B: For key heads Ø > 23 mm, thickness < 3.1 mm
• Variant C: For key heads Ø > 26.5 mm, thickness < 3.6 mm
  Each variant is available in two versions:

1. With integrated pen & toothpick slot
2. Without pen & toothpick

Print Information

• Filament: Works with any material (PLA, PETG, ABS, etc.).
• Supports:
  • All parts can be printed without supports,
  • Except the small end cap for the pen, which requires minimal support.
• Post-Processing:
  • After printing, remove the small integrated support structures inside the key slot using pliers.

This model is optimized for practical everyday use, slim form factor, and reliable carrying inside any standard wallet.