Length: 22 ft 2 in (6.8 m)
Width: 4 ft 11 in (1.5 m) Interior
Height: 5 ft 4 in (1.6 m) Exterior
Number Built: 10

High Pressure air charging
Battery ventilation valve
Battery charging point
Wooden rails for trolley bogey
Securing bar and holding down strops

Type DNC.A.2152/18 fitted forward on Trooper, Thrasher, Trusty, Turbulent and P-311. Type DNC.A.2149/18 fitted aft on Thrasher, Trusty, and Turbulent.
Type DNC.A.2151/18 fitted aft on Trooper. Type DNC.A.2158/18 fitted aft on P-311.
Type DNC.A.2150/18 fitted aft on Thunderbolt, Truant and Trident.
Type DNC.A.19/19A fitted aft on Taku.

Submarines additional ballast with their Q tanks full.
Three containers 9.5 tons of ballast added to the keel aft of amidships.
Two containers 3.5 tons of ballast added to the keel aft of amidships.
One container to remove 3.76 tons of ballast forward of amidships.

Built by Stothert and Pitt (Crane Makers) at Bath.