Lambro 6-Inch White Plastic Wall Cap

The Lambro 351W gives you a spring-loaded damper in a UV-resistant HIPS plastic wall cap that handles both exhaust and fresh-air intake applications. The 6-inch diameter fits standard round ducts, and the spring-loaded damper stays closed when not in use to prevent backdrafts and outside air entry. For HVAC contractors and builders working bathroom exhaust systems or fresh-air intake vents, it’s a versatile solution that doesn’t require separate inventory for different applications.

Spring-Loaded Damper and Dual Functionality

The damper mechanism sets this cap apart from basic louvered vents. It stays closed when not in use, which matters when you’re trying to keep Montana’s winter air out of finished spaces. The damper can be removed for fresh-air intake applications — useful when you’re meeting combustion air requirements for gas appliances.

Applications include bathroom fan exhaust venting, range-hood exhaust venting, general moist-air/humidity venting from the home, and fresh-air intake for homes with gas appliances. That flexibility means contractors don’t need to stock separate caps for exhaust versus intake applications. One SKU covers both needs.

The hinged removable screen prevents birds and large insects from nesting and comes out easily for cleaning. Anyone who’s pulled a bird nest out of a bathroom exhaust knows why this matters.

HIPS Construction with UV Protection

The High Impact Polystyrene (HIPS) plastic includes UV inhibitor to resist fading and sun damage. Montana’s high-altitude sun beats up unprotected plastics faster than most regions. Standard white plastic turns chalky and brittle after a few seasons. The UV inhibitor extends the working life considerably.

The material choice also makes field modifications easier. The cap can be painted with plastic-compatible paint (surface preparation required), and the caulk-friendly frame is designed for easy sealing during installation. No special primers or adhesion promoters needed — just clean it, scuff it, and paint it to match the siding.

Installation and Specifications

Specification	Value
Duct Size	6 inches diameter
Material	HIPS plastic
Color	White
Package Dimensions	9.5 x 6.5 x 10.125 inches
Weight	1.40 lbs
Mounting	Wall mount over 6-inch round ducting
Compatibility	6-inch diameter round ducts (rigid or semi-rigid), suitable for vertical wall installations

Installation follows standard wall cap procedure. Insert the vent collar into the 6-inch duct opening, secure the frame using four screws through the pre-drilled holes, and seal around the perimeter with caulk. Required tools not included: installation screws, caulking/sealant, and plastic-compatible paint if painting.

Customers report the product is ‘heavy duty’ and the spring-loaded damper works effectively. The spring-loaded mechanism is reliable, and it’s commonly used as a replacement for older or broken vent caps.

The Bottom Line

The Lambro 351W works for contractors who need a reliable wall cap that handles multiple applications. The spring-loaded damper keeps cold air out when the fan’s off, and the removable feature lets you convert it to fresh-air intake when needed. HIPS plastic with UV protection holds up better than bargain caps, and the 6-inch size covers most residential exhaust applications.

Skip it if you’re looking for decorative appeal or need something that blends into high-end siding. This is utilitarian plastic that does its job without pretense. But for standard bathroom exhaust or makeup air applications where function matters more than form, it’s a solid choice that won’t have you back for warranty calls.

Frequently Asked Questions

Can this wall cap be used for dryer venting? While the applications list includes bathroom fan exhaust and range-hood exhaust venting, dryer venting isn’t specifically mentioned. The spring-loaded damper might restrict the high-volume airflow that dryers require. Stick with dedicated dryer vent hoods for that application.

Should the damper be removed for fresh-air intake? Yes. For fresh-air intake applications, the damper can be removed. Leave it in place for exhaust applications where you want to prevent backdrafts.

What’s the warranty on this wall cap? No specific warranty term found in product documentation. Lambro typically provides a limited warranty for manufacturing defects. Customers are advised to contact Lambro Industries directly for claim details.

How does HIPS plastic compare to metal wall caps? HIPS plastic with UV inhibitor resists fading and sun damage. It won’t rust like steel or corrode like aluminum, but it’s not as impact-resistant as metal. The plastic is easier to cut and modify on-site, and it won’t dent during installation.

What size hole should be cut for installation? The cap fits 6-inch diameter round ducts. Cut your hole to match your duct size — typically 6.25 to 6.5 inches for easy insertion of standard 6-inch duct.