Prime is a variable, non-indexed track. Each bank gives you a personal margin on Prime, most often a discount, which stays the same for the life of the loan. Because it is not indexed to the Madad, inflation does not change your balance. Prime can be repaid early without a capitalization fee, which makes it easy to refinance.
Prime counts toward the 66.66% variable cap of Directive 329. There has been no separate limit on Prime since 27 December 2020. Because the payment follows every rate decision, Prime suits borrowers who can absorb a higher payment if rates rise.
The pitfall is comparing Prime discounts on their own. A bigger discount on Prime can come with a worse rate on the fixed tracks of the same mix, so compare the total cost of the whole offer. The current Bank of Israel rate and Prime are on the rates page.
Example
Suppose the Bank of Israel rate is 3% (illustrative): Prime is then 4.5%, and with a margin of minus 0.5 your track pays 4.0%. On ₪400,000 over 25 years the payment is about ₪2,111. If the Bank of Israel raises its rate by 0.25 point, the track pays 4.25% and the payment becomes about ₪2,167, about ₪56 more.