
KeyGuard SL-590
Score: 80/100
Master Lock 5440EC
Score: 85/100Rankings

The Master Lock 5440EC is a portable, smart key lock box designed for realtors and property managers who need flexible, temporary access control. Its key strength lies in its Bluetooth connectivity and app integration, allowing for tamper and low-battery alerts. While it lacks the permanent stability of wall-mount options, it is ideal for short-term rentals and property showings.

The KeyGuard SL-590 is a wall-mounted, weather-resistant key storage lock box with a heavy-duty metal frame and large capacity for up to 8 keys. Its primary drawback is the risk of permanent lockout if the combination is forgotten. It is well-suited for realtors and property managers needing secure, fixed key access.
| Attribute | ![]() | ![]() |
|---|---|---|
8 keysbest | 5 keys | |
12.7 cmbest | 12.2 cm | |
11.43 cmbest | 8.3 cm | |
6.6 cmbest | 2.9 cm | |
| ↓ lower better | 0.54 kg | 0.5 kgbest |
— | 46 mmbest | |
— | 1 yearsbest |
Click an attribute name to sort · Green = best, red = worst (relative to this comparison)
| Attribute | ![]() | ![]() |
|---|---|---|
Durability & Environment(1) | ||
Weather Resistance Rating | weather_resistant | Weather resistant to -40° |
Installation & Mounting(1) | ||
Mounting Type | wall_mount | Portable over-the-knob |
Storage & Capacity(1) | ||
Key Capacity (keys) | 8 keys | 5 keys |
Design & Fit(3) | ||
External Height (cm) | 12.70 cm | 12.2 cm |
External Width (cm) | 11.43 cm | 8.3 cm |
External Depth (cm) | 6.60 cm | 2.9 cm |
Build & Design(2) | ||
Body Material | metal | Molded body with vinyl-coated shackle |
Product Weight (kg) | 0.54 kg | 0.5 kg |
Security & Access(1) | ||
Lock Type | pushbutton | 4-digit combination |


Products in the top-left offer the best value (high score, low price).

Professional reviewers at CLKsupplies commend the KeyGuard SL-590 for its robust heavy-duty metal frame and impressive internal storage capacity, noting the effectiveness of the weather guard.
Everyday users and reviewers generally praise the product for its excellent storage capacity relative to its size and its durable construction that withstands outdoor elements.

Master Lock's official descriptions characterize the 5400D as a reliable key safe for home or rental use, emphasizing its secure, keyless access and anti-jamming design.
Official notes imply user-friendly operation and convenience for rentals and real estate, suggesting positive reception for its intended temporary access use cases.
“you can see how much space is still in here”


