Andy.
I have used a company in the past called Simply Bearings Ltd.
I have just looked on their website and typed in SH Bearing and the description of the product is as below:
Metal Shielded Deep Groove Ball Bearings: One of the most commonly used bearings, these types are manufactured with metal shields inserted into the outer raceway, these fit in closely to the inner race providing protection against light mechanical damage, some protection against the ingress of moisture, dust and other foreign matter and serve to retain the pre-filled grease in the bearing.
Shields can be removed for applications that only require 1 shield
Benefits: Provides light mechanical protection, limits moisture and dirt ingress, lubricated for life,
They have an excellent technical department so maybe worth giving them a call as they have a full range of bearings from economy to high end SKF etc.