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We manufacture metal cap seals, to protect all types of fastener heads by restricting access to the screw or bolt. Cup Seals are available in sizes ranging from small 3/8” diameter cups to large 1” diameter cups. These fastener protectors are ideal for sealing computer panels, engines, meters, and more.
Cup seals are two-part tamper-evident housings that snap over the head of a screw or bolt, making the fastener completely inaccessible without leaving visible evidence of tampering. The back piece is mounted over the fastener during installation, and the front cap clicks into place and self-locks. The only way to reach the screw afterward is to physically distort or destroy the cup seal, which makes any attempt at unauthorized fastener access immediately obvious. This matters because security screw bits are now widely available, making specialized screw head designs alone an unreliable deterrent.
Cup seals are available from 3/8 inch diameter up to 1 inch diameter to accommodate a range of fastener head sizes. They are offered in galvanized steel, brass, and copper, with multiple inner hole sizes to fit standard screw and bolt shank diameters including .189, .201, .250, .270, and .360 inch. Choosing the right cup requires matching the outer cap diameter to the space around the fastener head and the inner hole size to the shank diameter of the screw or bolt.
Yes. Cup seal tops can be printed with a company name, logo, or consecutive serial numbers. For higher security, both the top and bottom halves can be matched with the same number, creating a paired seal where any swap or substitution is immediately detectable at inspection. Numbered cup seals are particularly valuable for utility meters, calibration equipment, and engine panels where a documented seal record is required for regulatory audits.
To apply, insert the screw or bolt through the bottom hole of the cup seal back piece and tighten the fastener to its required torque. Then snap the front cap onto the back piece by hand until the self-locking mechanism engages, and record the serial number in your log. To remove, the cup seal body must be physically distorted or cut away, which destroys the seal and records the tampering. Replace with a new numbered unit immediately after the authorized access event.
Check that the front cap is fully seated and shows no signs of deformation, cracking, or forced separation from the back piece. Confirm the serial number matches your seal log for that piece of equipment. An undamaged cup seal with a matching number confirms the fastener has not been accessed since sealing. Any distortion, cracking, or serial number mismatch should be treated as evidence of unauthorized access and investigated before the equipment is operated.
Utility companies use cup seals on gas, water, and electricity meters to detect unauthorized bypass or adjustment. Fleet and transportation operations apply them to engine inspection panels and sealed powertrain components. Computer and electronics manufacturers use them on chassis fasteners to protect warranty seals and detect unauthorized internal access. Any metered, calibrated, or access-controlled system secured with a screw or bolt is a candidate for cup seal protection.
A version of the same cup seal used for fastener protection is also available as a highly secure wire seal. It features two small holes in the base through which the wire is inserted and attached inside the cup before closing. Though more costly than other wire seals, the cup seal's uniquely strong locking system makes it a sound choice for high-value and sensitive applications. It is most notably used with wire for securing locked containers in the transport and storage of precious metals and nuclear material.