Blister I and Blister II, so named for the problems they have when starting in cold weather, are small twin diesels who work on the Arlesdale Railway.
The Blisters are four-wheeled diesel tractors, and each has a Lister engine. They were bought for line construction in 1966, and have been retained for maintenance duties by the platelaying gangs and for shunting duties at Arlesburgh.
The nickname given them by the staff was perhaps inevitable. It may perhaps reflect starting difficulties on cold mornings, but in no sense decries their general power and utility.
The Blisters are based on Cyril, an engine who works on the Ravenglass and Eskdale Railway. Their trouble starting is based on the trouble experienced with the Muir-Hill Fordson granite tractors that worked at Ravenglass with stone traffic until 1953.
Blister I and Blister II are painted black with wasp stripes on their fronts and rears.