When I ordered my valve trim, Wayfair popped up that we needed this as well.  The price on this was great compared to other sites we saw and since we knew we were going to need this as we were taking a two handle faucet w/ tub filler and converting to a shower only with the valve trim, we pulled the trigger and just added this to our order.  I love that Wayfair reminded me we need it and had a much better price than other places!