MY frustration with MSC is their "up to" discounts.
The discount darkzero mentioned for example :
To save up to 40%, Enter Promo Code: MW40
To save up to 35%, Enter Promo Code: MRO35
Offer Valid 6/12/17 - 6/13/17
You need to click on an item to find out if the discount applies and the % discount - which is a % off some ill-defined catalog price.
For example, I go into the MSC site and get my "ENCO" prices. I click on an item, the discount is not from my ENCO price, but the price changes to this ill-defined catalog price and then the % discount. Sometimes the effect is zero, sometimes trivial. Rarely worth mentioning.