The Differences between Edge Trim, Bulb Seals, and Flab Seals

It can be complicated to choose the right type of seal that suits your purpose since they have many applications. Seals help join mechanisms together, preventing pressure and leakage. The effectiveness of a seal highly depends on adhesion. Many seals are made from EPDM material because it provides excellent resistance to extreme weather, aging, and ozone. Though it’s not fire-resistant, the material can resist tearing and abrasion. Below are the significant differences between edge trim, bulb, and flab seals in terms of function, design and design types.




Edge trim is used to cover a sharp or unfinished edge on fiberglass or steel. They can also be used to give beauty to the finished product. Edge trims have decorative textures and finishes. They are used in scoreboards, parking mirrors, satellite dishes, golf carts, motorbike helmets, cabinets, and several applications, including machinery guards, hot tubs and spas, playground equipment, and computer cabinets and car seats. Bulb seals are designed to keep dust, water, and extreme temperatures out of certain areas. Bulb seals provide insulation and sealing for doors with corners that have radii. A flap seal is a versatile PVC trim fixed with an EPDM sponge Rubber flap that provides a safe seal in areas requiring weather and water resistance, such as in RVs, truck covers, and construction and agricultural equipment. These seals can maintain balanced loading pressure. They are inexpensive and long-lasting as compared to the edge trim and bulb seals.




The edge trim has a steel interior and an extruded rubber exterior. The steel interior gives the edge trim the clamping ability, while the outside plastic or rubber material gives it an excellent finished style. Since the interior is flexible, it permits it to be fixed around any radius without buckling or widening at the mouth. Trim seals come in various materials like Neoprene, PVC, vinyl, and the dense and sponge EPDM (ethylene propylene diene monomer). Many edge trims come with an aluminum core to eliminate rust in salty water.


Bulb seals usually consist of a compact and solid retainer section and a compressible bulb.

The mechanism of a bulb seal is to install the trim over the edge of the door. When the door is closed, the bulb compresses to form a tight seal between the door and the jam. This gives edge protection and a beautiful finished appearance. The bulb part of the seal is made of a sponge rubber that gives it the ability to seal and is also an irresistible compression set. Different compounds manufacture the bulb seal, but EPDM and TPEs are preferred. EPDM remains flexible even in inclement weather. Thermoplastic elastomers (TPEs) have remarkable resilience to climate and give greater impact strength, but they are costly and recyclable. The bulb seals have medium-density hardness and a classic round shape. To choose the proper bulb seal, two questions must be answered. One is what hardness and size are required to make a tight seal? And how will the seal be fastened on the application? For maximum sealing performance, the seal should be in the correct size and made with the required material.


Types of Design


There are different edge trim types, including decorative edge trim, Customized, sew-able upholstery trim, and edge guards. They are easy to fix.


There are several types of bulb seals, including taped-on bulb seals, glued-on bulb seals, steel clips bulb seals, and dual durometer bulb seals.


Flap seals have a metal clip that can hold and retain a permanent grip. Flap seals types include the trim-lock flap seal and the rubber flap seal.