Rosco Manufacturing has two product-specific deals running right now: 10% off the Sauce Pack Barrel Bundle and 8% off the Upper Receiver Group. Both are solid savings for shoppers buying these particular items, so your choice depends on what you're planning to purchase.
If you're buying the Sauce Pack Barrel Bundle: The 10% discount applies here, making this the better option if that's your target purchase. You'll save more on this bundle than you would on an Upper Receiver Group with the 8% offer, so stack your cart with this item and take the larger percentage reduction.
If you're buying the Upper Receiver Group: The 8% off deal is designed for this product, so that's the offer to use. It's a straightforward saving on a core component.
If you're a first time customer with no specific purchase in mind yet: Signing up to Rosco Manufacturing's newsletter can put you in line for future special offers and promotions. This is worth considering before you shop if you think you might browse around and need time to decide, since newsletter subscribers often unlock additional deals you wouldn't see otherwise. Just make sure you've decided what to buy before heading to checkout, because the newsletter signup won't combine with the product specific discounts.
Only one offer applies at checkout, so compare what you're actually buying against the available discounts and go with whichever saves you the most on your basket. If you're torn between the Sauce Pack and the Upper Receiver Group, run the math on each: the 10% deal will almost always beat the 8% offer unless the Upper Receiver Group is significantly more expensive.