Backflow Protection:

A closed system pump has a barrier between the milk collection kit and the pump mechanism to prevent contamination by bacteria/mold/viruses/etc. An open system pump has no such barrier.

It is NOT possible to completely sterilize the inside of an open system pump - you would have to dismantle the pump to get to all the parts that could be affected, plus some of these parts are impossible to completely sanitize. Buying new tubing, new parts, and cleaning every cleanable part does NOT sanitize the motor of the pump, which (in an open system pump) is, by definition, open to the new milk you are pumping.

The silicon massager can provide extra stimulation to produce more milk, and makes the shield more comfortable.

The Who code is a  marketing code that aims to protect breastfeeding, to protect all mothers and babies (whether breastfeeding, formula-feeding or combination feeding) and to prevent aggressive marketing practices. Infant formula, feeding bottles, and artificial nipples are the main products that fall within the scope of the Code. Pacifiers and breast pumps are not under the scope of the Code, though the code violating companies sell Breastpumps, so they are labelled violators. 

Single Electric Pumps 

Double Electric Pumps