SunShader currently has a 12% off voucher at the top of this page, which is the main promo to use and is best for standard single orders where you want a straight percent off. The voucher must be entered at checkout and works on website orders, so it suits any purchase that is not a bulk or sale specific deal.
Small orders under about $25 or first time buyer: if this is your first order, the $3 off first order code may save you more than a percentage on a very small cart. For example, on a $20 order the $3 off reduces the total to $17, which is a $3 saving; the 12% code would save $2.40 and leave you with $17.60, so the $3 off is better for that first order.
Typical single purchase $25 to any mid size order: use the 12% off voucher at the top of this page. A 12% percent discount reduces most mid size carts more than the 10% code and will usually beat the fixed $3 unless your cart is very small. For example, on a $120 order the 12% code takes $14.40 off and brings the total to $105.60, while the 10% code saves $12 and the $3 first order does not apply unless it is your first order.
Very low spend where no code applies: if you are not a first time customer and your cart is under about $10, neither percent saves much; still use the 12% code if you can enter it at checkout.
Buying sale items: sale items carry their own markdowns, and the clearance sale offers up to 50% off sale products without a code. If the item you want is marked down in the clearance, the sale price can beat the 12% code. For example, a product reduced from $200 to 50% off sale price becomes $100; 12% off that would be additional only if the site allows stacking, which the sale terms do not promise. Use the sale price directly when the item is listed in the clearance.
Bulk purchases of SunShader Eco or Pro 5: the quantity deals are the best option when you meet their unit thresholds. Buy 10 units and you get 15% off; buy 50 units and get 30% off; buy 100 units and get 35% off; buy 500 units and get 40% off. These discounts apply on the qualifying bulk purchase of those models and are presented as sale offers, so they will usually beat the 12% code for the same items.
Choosing between offers: for a single non sale item, try the 12% off voucher at the top of this page first, because it gives a larger percent than the 10% code. If you are a new customer with a very small cart, use the $3 off first order code. If the item is in the clearance or the order meets a bulk threshold, take the listed sale discount for that product or quantity, since those sale rates are applied to sale items and to the specific bulk units and will typically leave you with the lower total.