BS 6121 Part 1 type designations A2, BW, CW and E1W sit on a single decision axis: armoured versus unarmoured cable, then whether the application needs an outer sheath seal, then whether the environment is dry indoor or weather-exposed [S6].
Across brass gland makers, the four types cover roughly the full BS 6121-1:2005 industrial range, with metric entries from M16 to M90, NPT or PG threads, and finishes in natural or nickel-plated brass [S1][S5]. Selection reduces to four questions, in order: armoured or not, indoor or outdoor, IP target, and cable diameter band [S3].
A2 / A1: The unarmoured-cable baseline
A2 is the only one of the four specified for unarmoured plastic or rubber-sheathed cable, with displacement sealing on the cable outer sheath and no armour clamp [S1][S5]. The Raychem RPG A1/A2 datasheet gives IEC/EN 62444 design, IP66 ingress, M20 to M90 metric thread options, and operating temperature of -40 to +100°C on neoprene seals or -50 to +135°C on silicone seals [S5].
Typical clamping range for an M20S A2 gland is 8.5 to 12.0 mm cable outer diameter, with 20 mm across-flat hex and 15 mm entry thread length [S5]. Use A2 when the cable has no armour braid or tape; if a steel-wire-armoured (SWA) cable is specified, A2 cannot provide earth continuity through the armour and is mechanically wrong for the job [S3].
BW: Indoor armoured, no outer seal
BW cable glands are designed to BS 6121-1:2005 and IEC/EN 62444, with a two-part armour lock, no outer sheath sealing, and IP2X as the rated level of protection [S5]. The fundamental difference between BW and CW glands is the outer sheath sealing arrangement, while both retain the armour mechanically [S2].
BW application is dry indoor, for use with all types of SWA cable, plastic or rubber sheathed; finishes are natural or nickel-plated brass, size range 16 to 90 (S and L) [S1]. A typical M25S BW clamp accepts 19.5 to 24.5 mm under-armour diameter at the armour cone, with a 31 mm across-flat hex and 10 mm entry thread length [S5].
CW: Armoured with outer seal, the workhorse
CW cable glands add an outer sheath seal on top of the BW-style armour clamp, which lets them serve outdoor or indoor armoured applications, with the outer seal providing the IP rating the BW lacks [S1][S3]. Standard reference is BS 6121 Part 1, sizes 16 to 110 in S and L form, natural or nickel-plated brass [S1].
Selection tip from the August 2026 BW-vs-CW guide: pick CW whenever the cable enters a weather-exposed enclosure, a washdown area, or any zone where the outer sheath could wick water past the armour braid [S2]. Accessory stacks also tend to be larger: earth tag, PVC shroud, neoprene or LSF rubber washer, PVC washer, and brass locknut are typically quoted together [S1].
E1W: Weatherproof single-armour gland
E1W type cable gland is specified for single-armoured SWA cable, plastic or rubber sheathed, and is described as weatherproof and waterproof for outdoor or indoor service [S1]. It carries the same two-armour locking principle as CW but with a heavier-duty outer seal arrangement tuned for permanent weather exposure [S3].
Standard reference BS 6121 Part 1, finishes in natural or nickel-plated brass, with all common accessories (earth tag, PVC shroud, neoprene or LSF rubber, PVC washer, brass locknut) listed as options [S1]. In practice, E1W is the default pick when CW's IP rating is borderline for the installation, and the project wants a single gland that covers both indoor risers and outdoor terminations on the same SWA run [S3].
Selection matrix across the four types
Comparison on four decision criteria, drawn from the BS 6121-1:2005 datasheets and the August 2026 selection guide [S2][S5]:
Cable type compatibility: A2 is unarmoured only; BW, CW and E1W are all for armoured (SWA) cable. IP rating: A2 reaches IP66 with a displacement seal on the outer sheath; BW is rated IP2X, dry-indoor only; CW adds an outer seal suitable for outdoor enclosures; E1W is the weatherproof option for permanent outdoor exposure [S1][S3][S5]. Thread and size range: A2 runs M20 to M90, BW runs M16 to M90, CW extends to size 110 in some maker ranges, all available in metric, NPT or PG thread forms [S1][S5]. Earth continuity: BW, CW and E1W all clamp the armour, providing the low-impedance earth path required for SWA; A2 has no armour to clamp and relies on the cable's own earth conductor terminated inside the enclosure [S3][S5].
Sizing against the SWA selection chart
For SWA cable, the brass gland selection chart cross-references conductor size, core count and overall diameter to gland size; a 4-core 10 mm² SWA at 20.3 mm overall maps to gland size 25 across all four armoured-compatible types, while a 4-core 70 mm² at 37.7 mm jumps to size 40 [S4]. That same chart shows the practical upper end: a 4-core 400 mm² SWA at 78.1 mm overall needs a 90 gland, and several combinations in the 95 to 240 mm² range are marked N/A in the smaller size columns, meaning the cable is too large for the smaller gland and forces a step up [S4].
Engineers should size the gland to the cable's bedding (under-armour) diameter for the armour cone and to the overall diameter for the outer seal, then confirm the maker's min/max figures against both before ordering [S3][S5]. Skipping this check is the most common reason a CW or E1W arrives on site and fails the IP test.
Accessories, threads and standards discipline
A complete, sealed installation usually needs more than the gland itself: locknuts, sealing washers, entry-thread reducers or adaptors, shrouds, and earth tags, and ordering these together avoids the classic "gland arrived but we are missing the washer" delay [S3]. A1/A2 datasheets list locknut, earth tag, shrouds and IP washer as standard accessories, with adaptor and reducer as additional items [S5].
Thread form matters: metric ISO entry threads dominate European panel-building, NPT is standard on North American enclosures, and PG remains in legacy German and Indian specifications [S1][S3]. The four types are mechanical designations, not explosion-protection certifications; for hazardous areas, an Ex-rated gland (flameproof Ex d or increased-safety Ex e) must be specified instead, and the broader ATEX/IECEx certification logic is covered separately in process-equipment guidance.
Limitations and what each type cannot do
A2 cannot terminate SWA: there is no armour clamp, so the steel braid would be loose at the entry and earth continuity through the armour is lost [S3][S5]. BW cannot be used outdoors as supplied, because it has no outer sheath seal and is rated IP2X; water tracking along the cable will reach the enclosure [S2][S5].
CW will not reach the IP rating of a fully weatherproof E1W in prolonged immersion or sun-exposed vertical runs, and on very large SWA the standard size range stops at 110, beyond which a maker-specific or custom gland is needed [S1][S3]. E1W is single-armour; for double-armoured (SWA + STA) cable, a different designation outside the A2/BW/CW/E1W set is required [S1][S3].
None of the four is a substitute for an Ex-certified gland in Zone 1 or Zone 2 classified areas, regardless of how good the IP rating looks on paper [S3]. For the broader certification logic when hazardous areas are in scope, see the ATEX/IECEx process-equipment comparison.
Trackable signals for the next quarter: BS 6121 Part 1 revision activity, IEC 62444 updates affecting displacement-seal test methods, and the ongoing migration from PG to metric threads in Indian and Middle-East panel-build specifications.
Component reference pages worth checking: cable gland, gland packing, and cable tray.
This topic is covered further in 16-bit vs 24-bit ADC in a Data Logger: When Resolution Pays Off.