No- they were aluminum discs about 1" OD x 1/2" thick with a single hole thru them. Your black plastic ones sound like substitutes, which is fine as long as they are rigid enough to keep the rails up off the soft carpeting.
Its possible to use wide, flat metal spacers such as yours to shift the passenger seat and its rails towards the door, which along with some fiddling with the steel firewall door blister, can allow the right seat to move much further back for more (skewed) leg room.
One problem seen with seat customization is, the metric seat bolts may extend further thru the welded nuts in the floor, such that the exposed ends get banged up and won't thread back thru the nuts. Trying with a bigger wrench sometimes breaks the nut-welds free, causing much effort to fix. Loose seats aren't safe nor comfortable.