Choose a safety padlock by checking shackle material, diameter, inside width and clear height together. PROLOCKEY’s P25, P38 and P76 drawings show 25 mm, 38 mm and 76 mm clear heights, with steel and nylon options. A longer shackle provides more reach; it does not automatically make a lock more suitable for every isolation point.
Two padlocks can look similar in a catalog and behave differently when passed through a breaker lockout or a multi-lock hasp. A useful selection process begins with the actual device and its available space, then checks material and environmental requirements.
Steel shackle or nylon shackle?
In the P series covered here, the S models use a steel shackle and the P models use a nylon shackle. The supplied product sheets describe a reinforced nylon body for both versions. Body material and shackle material should therefore be recorded separately.
| Selection point | Steel-shackle version | Nylon-shackle version |
|---|---|---|
| Models in this comparison | P25S, P38S, P76S | P25P, P38P, P76P |
| Shackle material | Steel; supplied sheets describe a chrome-plated finish | Nylon |
| Electrical conductivity of the shackle material | Metal is conductive | Nylon is a non-metallic insulating material |
| What still needs checking | Fit, finish, exposure conditions and the site specification | Fit, material grade, exposure conditions and any required electrical test evidence |
| What appearance cannot prove | Mechanical or corrosion performance | A voltage rating or permission for energized work |
Select a steel shackle where it meets the site’s material requirements and the intended device. Where the site specifies a non-metallic shackle, assess the nylon option against that requirement. Avoid treating either material as a universal answer for every electrical or mechanical task.
A nylon shackle is not an electrical work permit. For work covered by U.S. OSHA’s electrical rules, deenergization and verification requirements remain applicable. 29 CFR 1910.333(b)(2)(iv) addresses verification by a qualified person. Do not infer a tested voltage rating from material or product color.
Compare the 25 mm, 38 mm and 76 mm P-series dimensions
The following nominal dimensions are transcribed from PROLOCKEY’s P25S/P25P, P38S/P38P and P76S/P76P product drawings. Measurements are in millimeters.
| Model pair | Steel version | Nylon version | Clear shackle height | Inside shackle width | Shackle diameter | Body width × height × depth |
|---|---|---|---|---|---|---|
| P25 | P25S | P25P | 25 | 20 | 6.2 | 37 × 45.5 × 20 |
| P38 | P38S | P38P | 38 | 20 | 6.2 | 37 × 45.5 × 20 |
| P76 | P76S | P76P | 76 | 20 | 6.2 | 37 × 45.5 × 20 |
The height is the usable internal space shown in the drawing, not the padlock’s overall height. The diameter shown in these drawings is 6.2 mm; confirm the approved dimensions and tolerances for the order, particularly when the device opening is close to that size.
Measure the opening before choosing the height
Record the opening’s usable diameter or slot width, the thickness of the parts the shackle must pass through, and the space available around the body. Check the intended path of insertion rather than measuring only the opening from the front.
A hole that appears to accept a 6.2 mm shackle may still be difficult to use if the device is recessed or the padlock cannot rotate into position. A hasp may also need room for neighboring workers’ locks. Check that the padlock can close fully, that its key can be operated, and that the installed lock does not interfere with the device’s locking function.
Send the supplier a front view, a side view and an opening measurement. A photograph with a ruler can help establish clearance, but a trial fit is stronger evidence than estimating from a photo alone.
Choose the shortest height that satisfies the application
25 mm: assess this option where the shackle needs to pass through a compact lock point and there is enough space for the body and key operation.
38 mm: assess this option where the compact version cannot bridge the required thickness or clearance. It offers more internal height while retaining the dimensions shown for the body and inside width.
76 mm: assess this option where greater reach is needed around a deeper or less accessible lock point. Check its installed position carefully; the extra height does not solve an undersized hole or unsuitable device geometry.
These are selection questions rather than fixed assignments to particular industries. “P76 for all valves” or “P25 for all breakers” would be an unreliable rule because the relevant lockout device and installation space vary.
Keep the rest of the specification consistent
After confirming the shackle, specify keying, keys supplied, identification and color. A correctly fitting padlock can still be issued incorrectly if its key belongs to the wrong KA group or its label carries the wrong employee ID.
The product materials also describe a key-retaining function: the key remains captured while the shackle is open. Verify the selected configuration on the sample and include it in the order specification. Do not assume all padlock designs or other product families have the same mechanism.
For chemical exposure, temperature limits, corrosion resistance or dielectric requirements, request evidence for the exact model and conditions. Material descriptions alone are not a test result.
Frequently asked questions
Is shackle height the same as overall padlock height?
No. Clear shackle height is the usable internal height above the lock body. Overall height also includes the body and shackle material.
Will a 76 mm shackle fit where a 25 mm shackle does not?
Only if reach is the limiting factor. The P-series drawings show the same nominal diameter and inside width across these three heights, so the longer version does not solve every clearance problem.
Can I choose by “steel” or “plastic” alone?
No. Confirm the specific material, dimensions, environment and intended lockout device. Record body and shackle material separately.
Find the corresponding PROLOCKEY models
Compare P25S and P25P, P38S and P38P, or P76S and P76P.
Send an opening measurement and installation photographs to PROLOCKEY for configuration review. Then use our keying-system comparison to complete the key-control specification.
Source and scope: dimensional values and model materials come from the manufacturer drawings used for this comparison. The OSHA electrical-work reference applies within its U.S. scope; this article is a product-selection guide rather than an equipment-specific work procedure.