This has got to be the most impressive peak in the Hex River range, although perhaps the sheer cliffs of Milner Peak, 1995m, may also stake a claim. But for its domination of the surrounding landscape, there are few peaks like it in this part of the country. Mostertshoek Twins lies isolated at the Western end of the Waaihoeksberge section of the Hex, joined to Waaihoek Peak and the rest of the range by a long, sometimes knife edged ridge. The peak is made up of two summits, the Southern at 2031m and Northern at 1954m. Normally one would just climb the higher summit, which is slightly easier to reach. As one gets closer to the base of the peak, numerous pinnacles of rock seem to rise up to guard the mountain, making it a truly awesome sight. The peak is seldom climbed in comparison to its neighbour Waaihoek, and is also a somewhat more difficult peak to climb.
The normal route follows the path up to Waaihoek (for more details look at the Waaihoek page), and after climbing or skirting around Waaihoek Peak, one descends into a steep gully before climbing out to the left along the knife edge ridge. The gully is used to avoid the most difficult and precipitous part of the ridge. After these early sections the ridge is quite easy, and the route crosses back and forth over the ridge making use of the easiest ground on either side. As one nears the foot of the summit pyramid of the peak, the ground to the right of the crest of the ridge becomes fairly level and very pleasant going. Once at the foot of the pyramid you will realise that there is a large pinnacle between you and the peak proper. Follow the cairns into a fairly obvious gully on this pinnacle and climb up to near the top. You can now climb up a narrow gully, which could almost be described as a chimney, this will take you to the top of the pinnacle. From the top you will have to descend an equally narrow gully. To avoid both of these gullies, one can traverse to the right around the upper section of the pinnacle from just below the first narrow gully. Once off the pinnacle one can walk across to the base of the summit pyramid of the peak, and ascend into the large gully directly in front of you, still following cairns. It is advisable to stay in this gully most of the way until it opens out onto the summit slopes, the only time one should leave the gully is to avoid an overhanging boulder problem about two thirds of the way up. At this point the route veers out to the left briefly, then rejoins the main gully just above the overhang. Once up and out of the gully one simply needs to walk for about 15-20 minutes up the easy slopes to the summit. There is a lot of scrambling to do in the gullies on the pinnacle and the peak, though none of it is very difficult (nothing much harder than "B" grade, old South African grading), but some is just a little bit exposed and the ground is unrelentingly steep for this whole section. As you finish the scrambles take care to observe the surrounding features, you do not want to lose the route when you descend. It is not essential to hike all the way back to the Waaihoek path on the return, there is a cairn marking the GRASSY ridge off the main knife edge ridge which provides the simplest way down. Do not attempt to descend the first few ridges to your right on the return, and take a good look down the whole route to the bottom since you'll have to cross a few big riverbeds to get back to the Waaihoek parking. The whole hike and descent can be made in a full day by a fairly fit party, but always take some emergency gear and warm clothes as a precaution. You can also pay your money (a modest fee) and spend a night at the Hoare hut on Waaihoek Peak, and then make a more relaxed day of the hike, tagging Waaihoek Peak, 1948m on the way. There are other routes on the peak, such as "Green Gullies", which works its way up through the pinnacles and cliffs on the South side of the peak, quite a climb in winter. Check out the RD for details. For any winter climb on the peak, take a rope and some basic gear incase you need to abseil, since the gullies are likely to ice up.
A permit (costing about R20 / $3) is required from the UCT Mountain and Ski Club, there are hut fees for Waaihoek if you chose to spend a night, and a parking pass is a must, but all this is not going to seriously harm your bank account. Go to http://www.mountain.uct.ac.za/ to find the contact details of the huts convenor. Also ask about the security situation regarding where to park, since there have been car break-ins.
The descriptions above refer to a summer climb of the peak. In winter snow and ice will make the scrambles more tricky so great care should be taken, and only experienced mountaineers should attempt the peak in snow conditions. The mountain is of course slippery when wet, so consider this after rainfall.
Camping is allowed on the Zuurberg property, which now includes the hike up to Point Hi and across to Waaihoek Peak, although Mostertshoek Twins and the knife edge are not part of Zuurberg, so to camp you must backtrack to Waaihoek. There aren't many sheltered camping areas near Mostertshoek anyway. Hoare hut on Waaihoek Peak sleeps 20 or so and is well equiped, Pells Hut is smaller but fairly snug when its roof is on.
For weather forecasts, go to http://www.windguru.com/int/, and do a spot search for "Ceres", as this is the nearest town. Remeber, weather can change very fast in the Hex. Always be prepared.